Recently I'd been asked to enable an RSS feed for my SOA category in TypePad. TypePad allows for the provision of custom feeds, but only though the Advanced Template Set functionality that comes with a Pro account.
Richard had done some thinking on this awhile back, and suggested using a Blogdigger hack to accomplish it. While Blogdigger can get the job done, I was a little reticent to use that solution. Firstly, who's Blogdigger, and when will they change their *ahem* API. Secondly, the Blogdigger hack doesn't allow much control over how the results are presented, particularly the title of the resulting feed.
Since I'd been looking for an excuse to try out Yahoo Pipes, this seemed the opportune time. In about 5 minutes I'd created a custom feed from my site that allows an SOA-category-only RSS feed for this site. Unfortunately, there's a known bug in Pipes that prevents this from being used universally, but hopefully that issue will be fixed before too long.
I also made a more generic one that allows you to configure the category and feed URL as parameters (either via the Pipes site, or on the feed URL directly), so you can try it on your own site. It should work on most TypePad sites (keeping the aforementioned bug issue in mind). No warranties are expressed or implied.
All of that to say, Pipes is and awesome example of what SOA and XML should be all about. You should be able to mix, match and connect these things nearly effortlessly.