A great resource for finding cheap items on eBay is to look for bad grammar. While eBay does provide a spell checker, many sellers do not seem to use it. By typing an alternative to the search words you use often, you may find listings that others have not found. I have uncovered quite a few deals using this tool. While this may not work 100% of the time, it can actually be very amusing. In one such case, I contacted a seller to inform them of their mistake and may have saved him lots of money in listings. He was very grateful.
Below are some of my favorite searches and others that may be useful to you. Have fun!

Misspelled Listing Guide - Art & Jewelry

Lladro
Swarovski
Picasso
crystal
diamond
titanium
platinum
turquoise
rhinestone
pentagram
antique
vintage
nouveau
jewelry

I will be adding more categories as I think of them. Be sure to check back often.