Whether you buy or sell, it's a good idea to try and keep abreast of collecting trends online. Remembering that most people collect what they remember as a kid (tho not always), you'll find that's why things seem to fall out of favor as a new crop of collectors comes onto the scene.
I'm constantly surprised to see the high prices for things like frisbees, marbles, yoyo's, vintage tshirts, and the like.
On the other hand, things that used to sell for big $$ ten years ago have tended to drop in price.
Here's one item that suprised me:
Super Soaker Water Guns >
http://completed.shop.ebay.com/items...=p3286.c0.m282
How about you? Come across any interesting upward trends on eBay?