I'm building something right now that includes page parsing, and so far I've only been building in regex support. I like your jQuery selector idea as well, are there any other ways that you can think of that would make searching the contents of a page programmatically easier for you?
May I suggest taking a look at Parsely? Its the syntax they use on www.parselets.com. The documentation for implementing it in your own apps is a little sparse, but the data format is awesome. Here's one that describes scraping HN: