Where can i sell New & Used Textbooks online?  

You can at AbeBooks.Com... Try visiting thier site. I'll post the link for you.

http://buyback.abebooks.c...

I also sell books on line and my favorite place to list books is Half.com. It is affiliated with ebay, but is a separate operation. There are no listing fees and the commission is less than Amazon, so you net a larger percentage of the sale. However, The shipping reimbursement at Half.com is a bit less than Amazon, so this detracts from your total profit.
Half.com gives you the option of offering expedited shipping- many buyers like to use this, especially at the beginning of a semester. Consequently, a buyer might choose your textbook over a less expensive one in order to get it quickly.

There are a ton of plces online where you can get boks. The problem i that many sites will have the same book at a different price and comparing prices is timely. I've found that the best thing to do is touse a book price comparison engine, and the best site for this that I've found is www.wecomparebooks.com.
This site is great. They give youthe best price, and even tell you how much you save.
I've already saved hundreds on my textbooks!

I'm not all too sure... I know about a gazillion Dutch ones as I live in Holland and so I use these sites most of the time. Easy, because it saves me a lot on shipping and as most my textbooks are either Dutch of English but pretty much sought after in my country I allmost never need to sell on a foreign site when it comes to textbooks; new of used.

You might also consider local bookshops that sell secondhand books or buy them from people for their store. You allways get less money than online but the good thing is you have your money on hand instantly. However, if you are able to sell them online that's pretty much the way to get the most profit out of it.