Hi Blue,
There are a good number of inexpensive drives out there. Are you looking for a fast drive, or general purpose? If you are looking for a good general purpose drive, i have a couple of Maxtors that I have installed in some machines and they have been good general replacement drives... even use them for some iMovies. I believe you can get a 30 GB Maxtor for around $100...
good luck and I'm sure others will chime in with their experiences...
dave