Ebay can work well for getting rid of things. (I had a bidder on my Sim City cards, even!)
Some tips:
1) Write everything you want to say in the description of the item ahead of time, before you do the posting. Check similar items to see what sort of details you can include.
2) Take a picture of what you're selling, or find a picture you can use that's representitive. People like to see what they're buying.
3) Make sure you include as many correctly-spelled terms as possible in the title. If it's a D&D book like the draconomicon, I'd have it as 'D&D 3.5 Draconomicon D20' so that someone searching for d20 books will find it, as will people looking for both D&D and D&D 3.5. The more people who see your auction the better.
4) Don't bother with reserve prices, and put a low minimum bid out there if you really want to get rid of it.
5) Figure how how and how much shipping is for each item before you post them.
6) Post all your items at the same time. This way if someone likes the auction for 'The complete book of elves' then they can see that you're also getting rid of 'The complete book of half-orcs'.
Hope that helps!
John