I would argue that the races to watch for online campaigning innovations or qualitative impacts of internet-enhanced campaigns in 2006 is with state legislative primaries in open seats. The margins can be razor thin and candidates are close enough to the ground to measure the real-time impact of online campaigning. As they say, necessity is the mother of all invention.
State Legislative Primary Dates 2006 – From the National Conference of State Legislatures
If you know of excellent uses of online strategies by state legislative campaigns, open seats or not, add a link to that candidates site on the new DoWire wiki page – example online campaigns for state legislatures in the United States. This page will only grow with your input.