Get at tags for blog posts programmatically

I wonder how to get at tags in blog posts (WordPress, Blogger, or Blogspot) programmatically (API, RSS feed, XML, other methods). Preferably开发者_JAVA技巧 a solution usable in Ruby on Rails.

See what the life streaming Rails apps such as kakuteru are using. Tagging across multiple Web2.0 style streams is important to kakuteru and I think they may employ a number of techniques. The also employ zemanta which has an API to generate tags from content. You can see zemanta's example of getting tags using ruby

If either of those have an API, i'd start by reading their documentation; outside of that; you can roll your own screenscraper (which is likely to be useless, given the amount of DOM content that is script generated these days)

Wordpress API

Blogger API