For spam mail, there is currently only one application around; Antair BlackBerry Spam Filter
I will tell you up front, it's $50. That scares MANY people off. But if email spam is an issue, like it was for me (keyword being WAS), it's worth it. Support from the developers is second to none.
I've had the same email address for close to 10 years, gmail/yahoo/etc isn't an option. Whether I visited a "naughty site" or my address got mined off a messageboard, beats me; but for whatever reason, spam was a problem.
If you REALLY have a spam problem, $50 is nothing. If it's just an occasional annoyance, there are other solutions around (gmail or BIS filtering, etc.). I filter out Hotmail, Yahoo, Gmail, AOL, AIM -- that cuts out 90%+ alone (nobody I personally know has any of those addresses, and if they do -- I whitelist them).