Can anyone recommend a video camera or system for recording decent slow motion (i.e. high speed video) ? Something that will record at 500fps would be ideal and cheap also!! Are there any DIY solutions to this ?

I've got a feeling that "cheap" and "500fps" probably don't go together ;-)

See the following: http://www.dvinfo.net/conf/showthread.php?t=62933

Just about all high speed stuff is expensive and film.

However, here's a system that utilizes a bunch of cheap CCD cameras.

http://graphics.stanford.edu/papers/highspeedarray/