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://www.m0ukd.com/Calculators/Slim_Jim/index.php - Learn how to build your own "Slim Jim" or J-Pole antenna; includes a form to calculate the dimensions of the antenna you want to build

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

http://ohiosimplexnet.webs.com -  The Ohio Simplex Net

Software Defined Ham Radio Links:
A site for general info is naturally the Wiki site located here: http://en.wikipedia.org/wiki/Software-defined_radio

For more on interconnection to the internet by these radios you might try this link on WebSDR: http://websdr.org/

One other sort of generic link on the subject is here: http://sdr-radio.com/

Now then, for specific items, these are links for products that are either kits or ready to go systems. The most popular and best selling transceiver systems are Flex: http://www.flex-radio.com/

These folks are newer on the scene and I don't know much about them but the idea is a good one. Kits of mostly board sets that can give you a lot of variety in the system you would build yourself: http://www.nuand.com/blog/shop/

And then there is the FunCube. A very popular system for experimenters for several years now. http://www.funcubedongle.com/

The last item would be this item from NooElec. They realized that there was no HF capability for the inexpensive DVB-T USB devices so they made an up-converter for them. This allows you to use any of the kit or cheaper DVB-T sticks from eBay as the start point and with the up-converter you can listen to HF.
http://www.nooelec.com/store/software-defined-radio/ham-it-up-v1-0-rf-upconverter-for-software-defined-radio.html

Other suggestions:

- Check the equipment manufacturer's web page if looking for technical specs, manuals, etc.