Here are some resources (in random order):
Rogue Wave's STL Guide:
www2.roguewave.com/support/docs/sourcepro/edition9/html/stdlibug/index.html or stdcxx.apache.org/doc/stdlibug/index.html
The STL FAQ: butler.hpl.hp.com/stl/stl.faq
Kenny Zalewski's STL guide: www.cs.rpi.edu/projects/STL/htdocs/stl.html
STL Newbie's guide:
academic1.bellevue.edu/cpphome/stl/STL_newbie.html
SGI's STL Programmer's guide: www.sgi.com/tech/stl/
There are also some books that will help.