Overstreet's Price Guide has been the "Beckett" for comix since the '70s.
Available as hard-copy here:
http://www.gemstonepub.com/item.asp?ItemNo=59634
Available (slightly cheaper yet handier to use) as computer download here:
http://www.comic-book-collection-mad...verstreet.html
and here:
http://comics.ha.com/common/purchase...0&affil=473040
There's also this free (?) on-line price guide:
http://www.comicspriceguide.com/
Can't vouch for the accuracy of any prices listed in either source;
check completed auctions on eBay for real-world results.
If you find what you've got isn't worth selling
or keeping...
send 'em to us...