The evil spammers have websites listing blogs that are ripe targets for their filthy spam, so it's only fair that we also share ways to successfully beat them back into submission. I've been using Akismet pretty much exclusively on my blog since switching back to WordPress. It's been pretty good, but sometimes goes into "large-bore sieve mode" and lets in gobs of nastiness. I'd tried Mollom, and while it's interesting, it didn't have much luck against the particular flavours of spiced ham that get thrown at my blog.
But, I've found the combination of Akismet and TanTan's Simple Spam Filter plugin to be extremely effective. Here's my Akismet spam history graph. See if you can tell when I activated Simple Spam Filter...
November 13, 2008.
The graph doesn't show spam that got published, only spam that Akismet had to nuke. The number of spamments that were successful is quite minimal.
With the two working together, the amount of spam that actually gets through to be (temporarily) published on my blog is almost zero. Maybe one or two per day (sometimes slightly higher, sometimes none at all).