Swedish startup Twingly opened up its blog search engine to the public this morning. It now covers 30 million blogs, and results can be sorted by authority (number of incoming links) or most recent posts. There is also a spam-free search option that only brings back results from the hundreds of thousands of white-list blogs it knows to be real. (Read our earlier coverage, for more details).

It is hard for any blog search engine to take on Google Blog Search or Technorati at this point, but Twingly is givingit ago. And it’s European focus and translation features could help it carve out a niche.

CEO Martin Kallstorm highlights some of his search engine’s features on the Twingly Blog:

- Spam free search
- Social search. The users enhance the search results by voting on posts they like. Bloggers enhance the search results by linking to posts they like
- Subscribe to search results by RSS and alerts via email
- Language functionality: Translation of search results and filtering based on language
- Twingly widget platform. Parts of Twingly.com can be incorporated into blogs
- Hot Right Now. Overview on hot topics in the blogosphere
- User directed development through a tech plan open for voting.

Any search term can be subscribed to via RSS. Results can be voted up. And, best of all, users can vote on what Twingly should work on next.

Today, the company is also releasing widgets that blogs can put on their sites that show recent posts, recent links, and most linked-to posts. Here are examples for TechCrunch and you can create your own widget here.