You could use this?

http://www.makeymakey.com
 
A student of mine used this to make a highly entertaining dog bowl drum kit :)

Hmm, isn't this just as easily done on a keyboard controller? You use your fingers and its velocity sensitive and all that stuff. If you really have to use your hands then I guess you could re map sections of keys into parts. 
 

Maschine.

Quick question for the OP... what software are you using now (SONAR version, etc.)? You probably have simple tools already available, but may not realize it.

You guys are all brilliant, so thanks for some great suggestions. I should have clarified that I have Sonar X3
with Addictive drums, and I don't care much for pre-packaged MIDI drum clips, loops, etc. I went to a NAMM show to test out various controller boards, and the touch pads are way too small for my way of using hands.
 
I'm terrible with fingers, so I use my hands, especially the heel. From all these responses, the clever ones using
the makeymakey board, or the aerodrum, or the contact mic solution would really be fun to try!!!!
 
My daughter can help me bang out some great rhythms too!
 
I can't thank you all enough!

Technically, you should be able to bang rhythms on a table top and use Audiosnap to convert the transients into midi data.  You could then select the midi notes for each part and transpose them to the proper pitch in order to trigger a drum sample.  Or you could tap out the rhythms for each part one at a time and have Audiosnap convert them to the proper pitch during the same process.

This is where Ableton Live becomes so useful, more specifically Max4Live.
It's reasonably easy to create a M4L device that will map a midi note number to an incoming signal's transient, which can then of course be used to trigger a sample from a drum synth, AD2 for example.

I think it may even be possible to build a similar thing in NI's Reaktor…?

Downside is, it means having to learn how to program in Max and Reaktor, so er, not really ideal 
 
I think Mod Bod has the solution, purely because it's something you can do right away without having to spend anything and it will likely yield usable results.

The Roland Handsonic, might be worth a look.
 
http://www.roland.com/products/en/HPD-20/
 

Melodyne also has the ability to convert an analogue track to a midi track.

These are directions for how to do Mod Bod's suggestion.
 
1. Record yourself tapping on your guitar case or desk or whatever.
2. select the recorded clip and press A to open audio snap
3. In the right hand corner of the Audio Snap Pallet click the options button
4. Select Vary With Pulse Level in the Midi Extraction Section - this way your louder hits will be louder and softer taps will be softer after extracting the midi.
5. Change the track Edit Filter to Audio Transients in track view (it's on the track header as a drop down)
6. Move the Threshold slider in Audio Snap until your taps have transients in the right places
7. Next to the AudioSnap Power button there is a copy as midi button... copy your taps to midi.
8. Paste them into a midi track and route the midi to your favorite drum synth
9. select open Piano Roll view and select all the midi events and move them to the drum of your choice.
 
Melodyne is pitch sensitive. It does not create all of your taps at the same pitch necessarily (although you could probably manage it). Using AudioSnap should be simpler and work just fine.
 
If you don't get the velocity variation you are interested in, try normalizing the track before extracting the midi.