I do hard rock and metal, so I got Audio Assault Bass Grinder. It's pretty good for metal bass. There's also Cerberus from Kuassa which seems great for anything. For free, there is TSE's B.O.D., which is a Sansamp clone. One thing I
STRONGLY recommend is Studio Devil's Virtual Bass Amp, or Virtual Bass Amp Pro. I have Pro and LOVE it. Extremely flexible.
I just recently broke down and bought a Darkglass B7K as I'm getting more into hardware. I was broke for a bit after that, too. lololol