Online Mathematics Textbooks, a link list to higher math texts
http://www.math.gatech.edu/~cain/textbooks/onlinebooks.html

Online Statistics Textbooks
http://www.isixsigma.com/st/online_textbooks/

Comprehensive listing of freely available online textbooks for undergraduated and graduate Mathematics and Physics
http://homepages.nyu.edu/~jmg336/html/mathematics.html

Online Math & Science Texts
http://spot.colorado.edu/~dubin/bookmarks/b/1240.html

Textbooks, Lectures & Tutorials in Mathematics
http://www.geocities.com/alex_stef/mylist.html