Adam Kalsey: We’ve also added support for this to Pheedo, so in addition to inserting ads into your feeds, you can also easily USM-enable your feeds.
Randy: Adam's the first mover. 999 million bloggers, hosting services and clients to go. Adam also sent me a bunch of great ideas to improve the USM client. I'll add new aggregators. If you want your aggregator added to the USM client, then send me an email.
I also discovered that Pheedo has an awesome RSS marketing blog. Subscribed.