Things I've used to get enclosures and what I've used it for:
- HiFi tapedecks, tuners -> custom built hifi equipment
- SCSI storage controller -> RIAA amp
- UPS -> huge power supply
- jam jars -> kitchen timers
Just look around there's lots of things that can be put to good use for no or very little money. The local dump / recycling site is a good place to look for stuff (If they let you have it - our's don't, they're staffed with miserable, bossy OAP's who try to be as rude to you as they can get away with).