Here is a handy online guide for anyone involved in electoral politics online called the NetDemocracy Guide. The guide explains the differences between "uncompensated internet activity" that is exempt from regulation, and the kinds of "public communication" that require reporting as campaign contributions.
On a side note. This post comes from Micah Sifry, a journalist I respect very much. I’m happy to find out he is helping on newassignment.net, a project I’m watching and hoping is succesful.