http://www.fcc.gov - Find Part 97 rules on the Amateur service and renew your license
http://www.arrl.org - Lots of information for the beginning or experienced ham
http://www.rfcec.com - Information to self-teach yourself RF electronics principals
http://hamstudy.org - Practice ham radio tests
http://wwwdstarusers.org and http://www.dstarinfo.com - good resources on D-STAR technology
http://batteryuniversity.com - lots of information about how batteries work
http://www.ac6v.com - A clearinghouse of links to amateur radio and commercial sites
http://www.radio-locator.com - Resource for looking up information about AM and FM broadcast stations; includes transmitter info and signal patterns
http://www.rcgroups.com - Resource for all things radio controlled
http://www.techbyter.com - (Mostly) computer-related site produced by local ham Bill Blinn N8POV
Other suggestions:
- Check the equipment manufacturer's web page if looking for technical specs, manuals, etc.
- When all else fails, use a search engine such as Google to search for information