A friend of mine who also likes fountain pens put me onto a local auction house, Scammells, some time ago. The auctions are 9am on a Monday, so were rather inconvenient because I had to go to school and my funds weren't abundant, but I graduated a bit over a month ago and I've been going each Monday. They usually have at least one pen a week and you can pick up some great bargains. I won a Parker Slimfold there about 3 weeks ago for $30 that I've been using as my daily writer since, very nice nib. My friend got himself a Montblanc of some description in new condition for $70.
I rather enjoy the thrill of the bidding. They have all manner of interesting things there for collector types.
Does anyone else prow the local auctions for pens? I usually take a bottle of ink and give them a small test to make sure the nib is up to scratch, pardon the pun.