So far as I can tell, there are only three free, "lightweight", open source .Net blogging engines out there:

• dasBlog.  This is what my blog is using.  It's okay, but definitely lacking in some respects like proper XHTML markup, database post storage, and available plug-ins.  But it's completely free!
  
• Vine Type.  Looks good.  XHTML compliant (very much so that the source is almost not recognizable as ASP.Net source).  Unlike dasBlog, however, Vine Type isn't completely free; it's free for non-commercial use only (which is a very loose term nowadays in the blogging world with the explosion of AdSense supported blogs).
• Subtext.  Looks to be the least "feature rich" of the three (but I say this without having actually tried it).  Oddly, it's the only blogging engine whose site is not running off of the engine itself, which is somewhat disheartening.  Also lacking screenshots and examples, which makes it tough to get a feel for the features.

So are there other options available out there in the .Net space?  I dunno...looks incredibly lacking in all directions.

Random link (just because I feel like it, k?): A good discussion on Ruby on Rails and  .Net with some inspired commentary (don't skip the comments!).