MSN is slowly replacing Yahoo Publisher Ads (Overture for those old school folks) with those of their new MSN AdCenter program. The program is in BETA mode and not everyone can join.
You have to apply for the MSN AdCenter Beta Program.
I actually tooks a shot and signed on a couple weeks ago and today received an MSN AdCenter Invitation.
None of my ads are approved yet and I’ll have to edit this post later with a more thorough review.
At first glance I prefer the Adwords aministration setup but then again that’s the one I’m used to. Adwords has a nicer set of keyword suggestion tools. MSN AdCenter is not setup yet to be administered through the Firefox browser. You have to use I.E. There is also a non-refundable $5 charge if you are accepted and sign-up.
If you get in early, it ?might? be possible to find some high traffic keywords that have not been bid up yet. I’ll be looking for some of those. 
Have you received an invitation into the MSN Adcenter Beta Program? I’d like to here your thoughts.
By SEO Outline on 04-04-2006
April 5th, 2006 at 6:34 am
I haven’t gotten an invitation to MSN AdCenter yet. Then again I haven’t applied so that kind of explains it. I’ll be interested in what you find out about it though since I’ve been looking to start some PPC advertising in the near future.
I did however get accepted into Google Analytics earlier tonight. I had submitted my email 2 or 3 times over the last couple of months. Now I get the fun of adding the code to all my pages. Hopefully it will provde some good information that I;m not getting with the stats packages I currently have.