I've found some great stuff at Car Boot sales, we used to go to them all the time but less these days.
Amoungst the gems I got my first Amiga in about 2001, an A1200 for about £20

Recently I've picked up an A600HD for £4, Dreamcast + 10 Games for £8, Megadrive plus 10 games for £5, GBA for £1 lol
When I was collecting my sega saturn stuff originally I got most of the games for £1-£2
As Franko says you get the dealers there early but a lot of people are wise to it now and don't sell to them :hammer:
Anyway, a great way to spend a summers morning

Steve.