[lug] slightly OT: used tech book stores?

[Bear Giles]

Slightly OT -- are there good used tech bookstores in the area?  
(Including Ft. Collins).  I'm looking to sell some comp sci and applied 
math books.  On the other hand the combination of me, technical books 
and money is bad.  Very bad.

Slightly On T -- I have most of the O'Reilly series on X/Windows and 
X/Motif.  I know kids today prefer QT etc., but somebody might be 
working on older code.

Bear