I'll start by directing you to the website of the membership society for systems engineers: http://www.incose.org Their products and publications section has some publicly-available documents discussing various topics.

The Systems Engineering Body of Knowledge (http://www.sebokwiki.org/) would also be a good place to start. Probably quite a bit of overlap with the INCOSE site, but better organized.

OCW has a systems engineering course posted: http://ocw.mit.edu/courses/engineering-systems-division/esd-.... There are some lecture notes available, but unfortunately the materials are a little thin.