Frustrated by spam? Check out JunkMatcher.

"Apple's built-in Mail.app has a wonderful, statistically trained junk filter. Unfortunately, spammers nowadays use various tricks to conceal the real things they want to say (use of graphics, encoded characters, etc.). If you're going nuts about this, download the small tool I wrote, and follow the instructions below to use various effective techniques such as IP-based filtering, and flexible regular expressions to identify those sneaky junk mails."