To use a Star Wars analogy, sometimes you don't need an elegant weapon, so best to start with a blaster to wipe out the easy stuff, then follow up with a light saber for elegant, close up killing.
We've been using IP-to-nation tests as part of our spam blocking suite for almost two and a half years, and they alone typically catch 75% to 85% of all spam.
Ok, here goes, but first...
*** BIG Disclaimer ***
I extracted these via our anti-spam analysis tool, however exporting in .htaccess format is a brand new, not yet fully tested function, so these could be somewhat off. Note also that this is just a partial htaccess file and must be inserted into a "complete" one to work properly. Use at your own risk, etc. At the very least, this should be a helpful starting point:
The original data source is APNIC's public IP allocation records, which were downloaded at the beginning of this month. The extractor says the IP ranges contain a "total of 152,610,048 IPs" (wow!).
It's trivial for me to export any country, so if someone wants another one, feel free to ask.
P.S. Gratuitous plug:
By the way, the tool I'm using is a powerful anti-spam filter suite, written by a colleague, and discussed in some detail in this thread. In addition to light sabers and sledgehammers, it also comes with grenades.
We're setting up a DreamHost account mainly to expand our user base (we're planning to offer "free" small domains to a few friends, in exchange for in person usability testing of the upcoming web-based FP detection tools).
If it works fine here, other candidates for our spam killing Team will be welcome!