I've written an Automator workflow that will download the MVPS HOSTS file and place it in the /private/etc folder. The workflow can be saved as an iCal plugin to run automatically, and does most of its work in the background -- it does ask for a password when it replaces the old hosts file, though.
After downloading the Automator workflow (119KB: Original host • Hints mirror), open the desired workflow in Automator (one has Growl support, one doesn't) and go to File » Save as Plug-in. Select iCal Alarm, and now you can have it run once a week/month/year to help keep your Mac a little bit safer from unwanted internet intrusions. Please be aware that the workflow does not back up your old hosts file, so please be carfull when using it!
[robg adds: The workflow is relatively straightforward; it just curls the latest file from the site, renames it, and moves it into /etc/hosts. Be aware that the MVPS HOSTS file blocks a ton of sites, not all of which you may want blocked -- make sure you understand what you're getting if you use this hint.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20100423134359860