Thankfully, spam has been slow on my usual E-mail accounts as of recent. I dunno who to give credit though. It could be better blackhole lists, blacklisting by default of dynamic IP address ranges to block zombie bot spew, SPF records, or a number of things.
If you run an Exchange server fabric, Microsoft is extremely proactive with getting new heuristics out to servers, usually weekly if not more often. Exchange 2007 with its antispam rules is pretty thorough with catching stuff, although for enterprise/corporate use, I would recommend a third party A/V product like Symantec Mail Security for Microsoft Exchange.