A week or so ago I spent a few hours playing around with Yahoo!'s new mobile platform and created a Mowser Top Sites snippet for their new mobile home page. After getting it working to a decent degree, I submitted it and it looks like they approved it shortly thereafter and put it up in the catalog, though I only just noticed today that it was live! It looks pretty good, no?
In Yahoo! Mobile terms, a "snippet" is different from a "widget" in that like a Facebook application, it's a web-based plugin to their home page, whereas widgets can work on their Yahoo! Go 3.0 client as well. It won't take much work to get the Snippet markup to work on the client, actually, it just needs some "wrapper" markup, and the rest should be pretty simple. Now that it's live, I also need to go back in and make sure the XML is well formatted - there's a few pages that die because the feed content has passed through an invalid entity, etc.
The app is pretty basic, you just get a list of top categories which lead to lists of popular feeds, which leads to news summaries, which leads to Mowser.com adapted versions of the site. The categories are a clone of AllTop.com actually (in case you hadn't noticed), though as I tweak the app and feeds it should diverge quickly from their list so it's less of a rip-off. The other option was to use Mowser's 2,000+ top feeds which are all tagged, etc., but I was trying to go for a super-simple list in a straight hierarchy.
Like I wrote before - I really like the Yahoo! 3.0 web strategy. The new beta home page only works on a few advanced phones at the moment - like the iPhone and the n95 - but once it goes live, getting a cool Snippet to be popular could drive real traffic to Mowser (though Google is coming on strong, Y! still gets a *lot* of mobile traffic). The "Blueprint" SDK is a bit wonky, but it was easy enough to use once you put a few things together though the forms are definitely not for the faint of heart. I would have rather they just used a subset of valid XHTML-Basic instead - it would have been faster for developers, and probably easier for Y! to parse as well, but that's also why I don't work there any more. :-)
If you happen to be using the new Y! home page, definitely give it a try!