Once I have the 9+ Gb bootstrap.dat file downloaded, how do I use it? I'd like to attempt mining without joining a pool; do I have the right file for a solo effort? I can use Windows or Linux so either one in the answer will be fine.
When you run bitcoin-qt or bitcoind in command line, pass that argument. This way, the client indexes transactions from a file, not from the internet.
Source: http://eu2.bitcoincharts.com/blockchain/ Version 0.7 or later will also import this file by passing the command line argument "-loadblock=/path/to/bootstrap.dat" to bitcoin-qt or bitcoind.
I just did it in Windows. Download Bootstrap.dat, then look for C:\Users\Your Name\AppData\Roaming\Bitcoin and put the file there. Bitcoin will automatically find it and load from it. Good luck.