I ended up writing my own using SimplePie. Here's a multifeed demo: http://simplepie.org/wiki/tutorial/how_to_replicate_popurls

With the demise of many of the Craigslist national search apps, I ended up taking SimplePie into that realm and produced a 418-CLfeed search engine for personal use as a collector/hobbyist ...OK, hoarder. Works!