Here are my top 6 favorite antenna design resources (not necessarily in order):
#1) Modern Antenna Handbook edited by Constantine A. Balanis
If you are not in a hurry, you can get your copy for a reasonable price (I paid $45 for a used copy). Great reference covering a huge range of antennas with a lot of details. When you need more information, you can easily use the references to get more detailed information as a starting point for your design.
#2) Antenna Theory Analysis and Design by Constantine A. Balanis
Again, a great resource to use as a starting point for your design.
#3) Antenna Engineering Handbook by Richard C. Johnson and Henry Jasik
I use this as my backup when the two above don’t have what I am looking for. You should be able to pick one up at a very reasonable price.
#4) Defense Technical Information Center
One of my favorites. Contains a vast array of declassified research papers as well as symposium documentation on antennas and related subjects. Don’t forget this site as a great, free resource!
At the site try searching on “antenna symposium” in the upper right to see the wealth of information you can access.
If interested, I have collected and indexed (not quite complete yet) the “Antenna Applications Symposium” yearly held at Monticello, Illinois. The index is searchable for finding the volume and reference information for specific antenna topics.
#5) FEKO White Papers
Another great resource but more specific.
#6) IEEE
Costly, but helpful.
ARSI 