Edit: That didn't work, but a free application called ssdfanctrl did. Installed, restarted, set to "SMART" control and... completely silent. http://exirion.net/ssdfanctrl
This took me about 15 minutes. Watch step 7 the most; that display data cable is fragile, and you're going to need good lighting to see it.
If you're installing an SSD, you'll definitely need an adapter for it so it seats properly in the iMac's shell. I bought a Newer Technology AdaptaDrive 2.5" to 3.5" Drive Converter Bracket for $14, and it's of excellent build quality. Fits like a glove in there.
Finally, your fan is going to spin up like crazy after your first boot. Don't freak out just yet; follow these instructions after you've turned your computer on (from http://support.apple.com/kb/ht3964):
1. Shut down the computer.
2. Unplug the computer's power cord.
3. Wait fifteen seconds.
4. Attach the computer's power cord.
5. Wait five seconds, then press the power button to turn on the computer.
The USB part linked to here was too expensive for my liking ($43, ack), so I took my chances on this one. Was only $10. Add a full set of Samsung-ready tools for $7, plus $5 in shipping, and it's a steal.
Anyway, this took me about 10-15 minutes and was 100% successful. Thanks for the guide Sam Thompson. Saved me hundreds of dollars and hours of aggravation tied to replacing my phone because of a few bent microUSB connectors.
