I saw two Ron Paul TV ads last night on cable -- actually, the same ad twice on two different channels. It was on the History Channel and on ESPN, probably around 11:30 PM. (Good targeting of demographics!) It had Ron Paul speaking to a large crowd about liberty (I think it was from the Tennessee rally), with a floating image of the Constitution. It was run by "Patriots for Paul", not by the campaign, but referred people to the campaign website.
Good job Patriots for Paul!
I've heard several of the campaign's radio ads on talk radio, on the morning and evening drives, and I have a short commute.
The only TV ads I have seen for the election are the Indian gaming propositions (pro and con), and a lot of Hillary ads. She is advertising big time on HGTV and the Food Network, which my wife watches a lot. We have yet to see any Obama or Romney ads.