I have played RB 3 times now with a small group, and am interested in trying it solo. Is there any info on the most popular solo rules? Thanks in advance.

Check out:

Mr Skeletors Guide to playing Runebound Solo
http://www.boardgamegeek.com/thread/122763

on the Board Game Geek website.
He did a great job putting this together.

Besides covering the base game he includes guidelines for playing all the board and card expansions solo.

Thanks. Not sure how I missed that.

These are awesome rules and very simple to play with; and using his Threat Level idea (along with the use of playing cards as Threat Level/Difficulty) works like a charm. This is how I play solo, if I'm not using my own Doom Track variant. Plus with his modifications for all expansions, what more do you need?

I put in my first session with these rules yesterday. They are great and deserve all the praise!