Does anyone know a good online resource for learning piano. I've been playing guitar for many years. Now that I'm working with midi more often it would be nice to improve my knowledge on the keyboard. I'm looking to avoid learning stuff like Old McDonald and other kid songs so that I stay motivated to learn. Mostly I just want the basics for hashing out ideas. thanks

1st learn all the notes on the keyboard. Sit at the keyboard once a day working at it for 30 min or so. It will take time so don't set a limit just be consistent. After you get comfortable with all the notes move to diatonic chords n C cuz there are no sharps or flats. Triads and 7th chords. Stay with the 30 min sessions. 
 
I suggest this book 

If you're trying to learn how to actually play full on piano stuff I can't help you but for understanding the keyboard just so you can punch in basslines, chords and melodies try this stuff...
 
Learn the seven modes in C Major. It's all white keys so it's easy and the basic premise is you find the C. Play from C to C (and always remember where the C key is... doesn't even matter if it's middle C).
 
Then go up one white key (which will be D) and play from D to D. Just keep going up one key like that until you reach the next C. Those are the modes.
 
Then research the Circle of Fifths for the keyboard. It's wicked simple. Essentially it moves through all the Major keys. On guitar this is f*cked. On the piano it is soooper easy. You just add one black key every time in a specific order until you run out of black keys (just look it up). From there you can use those black/white key patterns to create all twelve keys and to create the modes you just do what you did with C Major (start on the first not, play up to the octave. Start on the second note, play up to the octave, and so on).
 
After you get used to that concept (you don't have to be proficient if you're just trying to understand the keyboard) then learn how simple triads (I III V) chords are fingered. Then how they invert (III V I or V I III).
 
Try playing those triads and their inversions in arpeggios. Move up the scales/modes of the keys to create different triad qualities (there are 3 Major, 3 Minor and  1 Diminished in the Major modes/keys).
 
Then add a 7th to your chords or whatever else you want. Just like guitar if you stick to those basic scales and modes you can't really go wrong. Of course you can mix it up with harmonic/melodic minors or exotic scales.
 
Really piano theory is about a million times easier than guitar theory IMO. It's all laid out for you right there on the keyboard. Actually PLAYING the piano... properly... with both hands? Well that is a whole other story but just twonking out some chords and melodies for MIDI input is no problem.
 
Cheers.

Back in 1964, I could play Mozart piano concertos, transcribing on the fly. Today, I look at my hands and wonder what the hell happened. 
 
If you want to learn to play the piano properly, or relearn, as in my case, check out the following:
 
http://www.amazon.com/gp/product/0882848186
http://www.amazon.com/gp/product/0882849956
http://www.amazon.com/gp/product/0739000683
 
This Adult All-In-One course is, IMO, the best of many. What can be confusing is that this course was designed to be instructor-led, so most of the listings are for the student book (without CD), not the teacher's book (with the CD). In this case, I didn't need the CDs; the series is that good.
 
Happy Keyboarding!
 
I've also found Keyboard Magazine to be one of the best written musician's mags. Always good stuff.

This is a tough question, but I will say I began playing piano as a child, and learned more about the piano by playing guitar than I did from any piano teacher.
 
Chords/intervals are all the same, the only difference is the spacing is now a bit off because the keys are not all the same size! This can make learning key signatures seem like a mathematical equation at times, so the hurdle for me has been learning keys and being able to move between them without "thinking." Initially that is a challenge, so easier to work in one at a time.
 
Advantage of a piano is that all inversions are possible (easily) with just one hand! From a "compositional" standpoint, it is similar to guitar to begin with (key) chords. One side point that is helpful is what I have seen called a "7-3-5" voicing (for sevenths chords), where the root is dropped by 2 octaves (into the bass line), and the 7th is dropped by an octave (so is a half step below the initial root). The root is then played left-handed, and the 7-3-5 is played with the right hand (only one key is different from the major triad). This yields a very full sound, and can readily play with the individual notes from there.
 
From a sonic perspective, playing with 2-note voicings (simple intervals) can be a great learning experience (same as on a guitar).

Since you play guitar, you should be able to teach yourself, at least to kick start. And the first step (when I got started) is to master the Major Scales in all 12 keys. Buy a scale book with fingerings. Go with the order of one extra sharp or flat at a time (circle of 5th) C, G, D.. / (circle of 4th) C, F, Bb.. Once you're able to play a full scale in a few keys, that would give you sufficient info how to position your fingerings and you can attempt any melody you already know.
 
And then this too :
 
http://www.pianopractice.org/book.pdf

I would recommend taking just a couple of lessons from someone in your area. They can narrow in on your knowledge of music, provide some quick insight as to how to understand the piano then give you a suggestion or two on books that can help you progress.
 

mettelus
This is a tough question, but I will say I began playing piano as a child, and learned more about the piano by playing guitar than I did from any piano teacher.

 
Might I suggest you didn't have a very good teacher, or teachers . A keyboard is a very easy instrument to understand compared to a guitar and therefore should be relatively easy to teach. (I'm talking about understanding the instrument, not becoming a great player on it...)
 
Example: Take somebody with zero musical knowledge and show them a C note on a Piano, and explain to them that the C note is always the white key before the two black keys. Immediately - they can point to every C note on a Piano. Or that all the white keys are the naturals (c,d,e,f,g,a,b) and the black keys are sharps/flats. That's not so easy to explain on the guitar.

Yeah, I will give you that one. I was also 8, and the focus was playing simple things and sight reading. When I help out others, especially new players, I typically head them down the path of (key) chords since that is the foundation for everything, and chords/vocal alone is often enough to perform a song (guitar has the advantage that you can take it with you ). Bottom line is it is incredibly easy to totally overwhelm someone new and leave them disheartened if they cannot go off on their own and actually "do something." So much about "instrument" is personal preference, and they all have their place or wouldn't exist.
 
Visually on a guitar, barre chords, intervals, etc. all have the same left hand position, just the root changes. Simply learning the notes on the E and A strings is a good start for new guitarists (hence power chords being so popular), and they do not even "need" to know what the other notes are to play them. I remember as a kid counting keys often to "find" major/minor triads.
 
The biggest hurdle to a new guitarist is actually pain in the fingertips... that hurdle has to be approached with care as some will give up forever as a result. I never recall my fingers ever hurting from piano...

All very useful recommendations above. One of the biggest difficulties I found was the relationship between the rhythm/bass playing of the left hand underpinning the  patterns of melody you are picking out on the right hand. Practise some basic left hand moves on their own, basic 1, 3, 5, 6 stuff, etc in keys of C, G, F. Add a basic simple melody - Mary had a little lamb, etc and just to familiarise yourself with these patterns.
 
I saw Jools Holland and his Rhythm and Blues Orchestra last week. Watching Jools is enough to make me wonder what I'm doing in front of a keyboard. Still ... we can all dream!
 
Jerry

I just stay away from those black notes.