I tagged this post under "etiquette" for lack of a better category, but this is one issue that is sure to be litigated in a variety of different contexts [Seattle Times] [link to decision]:

A state appeals court Monday upheld a state law that prohibits public employees from using any public facilities or resources for political activity.

The case involved two Ballard High School teachers fined by the state Public Disclosure Commission for using the school e-mail system to tell teachers to put completed petitions for two 2004 education ballot measures in a school mailbox.

To reiterate, at issue in the case is whether the teachers "used" public facilities or resources for advocacy purposes when they forwarded an email telling the other teachers that if they had any completed petitions, they would be picked up today. 

There are a variety (more like a plethora) of First Amendment issues and doctrines that are implicated by this case, including the appropriate test:  Pickering, Tinker, public forum analysis, strict scrutiny, etc.  For once, the question of whether cyberspace is actually "a place" is relevant (in which case it potentially triggers public forum analysis).

I don't have time to dissect these issues in depth, but the case is short and worth a read.  In the meantime, public employees should always always set up gmail (or other similar) email accounts and not use the "public" email to communicate on non-work-related issues.  Of course, this doesn't resolve the issue of whether use of the school server and computer constitutes "use of public resources," but that will have to wait for another case.