Anyone who either belongs to a list, or has a website is usually plagued by
spam. This would include most members of this list. While there are some
filters that just block messages in a fairly mindless fashion, some better
products have recently become available. For all systems there is a naive
Bayesian filter which can be added to any mail system. It is not well
integrated, although it works well. One of these is available at: http://sourceforge.net/projects/popfile/
I realize this is not physics education, but I consider it to be a service
for those of us who are plagued by spam. Incidentally it is possible to get
rid of a lot of it by requesting removal from the spammer's list. If they
advertise a web site to do this, it actually works.