The following article: “Getting Clueful: Five Things You Should Know About Fighting Spam” gives a great 50,000 foot (ok, maybe even 100,000 foot) level overview about spam-fighting. It’s got some great tips for IT folks to prepare for their next meeting with management.
One thing I disagree with, however, is the implication in the article that fighting spam requires ever-expanding budgets, due to the fact that spammers are always improving their techniques. This may be true for companies that try to make do with open-source or other low-end technologies, since they get stuck tuning and re-tuning their filters with each new spammer tactic. However for enterprise-class solutions, the vendor must responsible for maintaining high detection rates. This should part of the maintenance agreement between the enterprise and the vendor.