http://aces.ee.olemiss.edu/ Applied Computational Electromagnetics Society (ACES) Online
http://www.arising.com.au/people/Holland/Ralph/ VK1BRH page, antenna simulation
http://www.arising.com.au/people/Holland/Ralph/Antsim.htm - some interesting info, an article on sloping dipoles for instance.
http://www.ee.surrey.ac.uk/Personal/D.Jefferies/antennas.html - Univ of Surrey professor David Jefferies's great site with some good theory and explanations in practical terms.
http://www.ece.mcmaster.ca/faculty/georgieva/antennas.htm - Professor Georgieva's site - look at the lecture notes from previous courses.. recommended by Prof. Jeffries, above.
http://emlab2.nmsu.edu/classes/ee315/tl/tl.html - Steven Castillo's page for NMSU EE315, Transmission Line Analysis, has most of the usual equations.
http://emlib.jpl.nasa.gov/EMLIB/files.html - electromagnetics library at JPL, mostly commented links to other stuff
http://fermi.la.asu.edu/w9cf/articles/mutual/index.html - K.E. Schmidt (http://fermi.la.asu.edu/w9cf/)- Simplified Mutual Impedance of Nonplanar Skew Dipoles - I was using this as a basis for computing mutual Z, before I decided to bite the bullet and just fire off NEC to do the calculations each time.