Ask.com and Bloglines, which are both owned by Oakland-based IAC/InterActiveCorp, have added blog search functionality. I think the blog search results on Ask.com look better than that of Bloglines however, it turns out both Ask and Bloglines each has its own implementation of the same search functionality.
The Ask.com blog search is loaded with a number of features which include saving a search result, posting a search result to Bloglines, digg, del.icio.us or Newsvines and subscribing to the feed related to the search result. My favorite feature is the binoculars feature (similar to the binoculars on web search) which allows you to hover over the icon to see the details of a post without actually having to visit the blog itself.
Mike Arrington recently posted about the new search on TechCrunch and mentioned how it has been a longtime coming. In addition, Mike points to an issue with the way that many of the current blog search engines operate. For example, Technorati measure the authority of a blog based on the number of inbound links. This means that anyone with lots of inbound links can go into Technorati and post about something they are not familiar with (i.e. basket weaving) and become the instant authority.
The new Ask.com blog search engines does not appear to remedy this problem since it bases its rankings on the number of feed subscribers a blog feed has. Sphere, another blog search engine, which launched last month takes a different approach by creating digital fingerprint of every since piece blog content and then uses an algorithm similar to a Google page rank to determine relevancy. Therefore, I believe Sphere offers the most relevant blog search results.