Line 6, Waves, IK Multimedia and Native instruments all make guitar amp emulation software. Line 6 and NI also sell theirs with USB audio interfaces, I'd recommend the Line 6 toneport studio UX1 for simple bass recordings. It's fairly cheap and easy to use. In terms of a practice amp there are loads out there, look for something that has a headphone out socket on it and an aux in for playing other sound sources through the amp. The Roland Bass Micro cube RX is a great practice amp, it can run off batteries and has a tuner, metronome, effects, 3 band EQ and a compressor.
Hope this helps.