Somebody stole the back wheel off my bike. i want to replace it but am on a tight budget. will any 8spd wheel do?

No, if it's disc you need to make sure the hole pattern is the same if you want to be able to swap discs around (minimal setback). Then you need to get a disc that's the same size as the one you had because wheels don't normally come with the discs on them.

The rim width is not a BIG deal within reason. Try to match the remaining rim.

If it's a rim-brake style it doesn't matter so much.

In either case make sure it comes with a cassette body that is 8-speed compatible. Then you need a gear cluster.

http://sheldonbrown.com/k7.html

If the chain has significant miles on it you might as well get one of those too or it may be too worn to mesh properly with the new gears and it will prematurely destroy them if it works at all. Specify 8-speed as they come in different widths.

http://www.sheldonbrown.com/speeds.html

http://sheldonbrown.com/chains.html

http://www.parktool.com/blog/repair-help

Believe it or not, taking the bike to a shop and letting them replace the wheel will be the fastest and least expensive solution unless you already have the knowledge and special tools required for cassette and chain service.