Ruby on rails is on track for getting more popularity among casual as well as professional developers when they need to develop and release a small- medium size application rapidly. I myself find it very interesting and have the opinion that it is a good innovation, helping the developers avoiding the complexities of ASP.Net or Java based structures where they mostly need to develop apps from scratch with lot of plugging.
Now it is more interesting to read about the ASP.NET MVC framework, going to be released in the first half next year and also will be a part of .Net 3.5 SP1 . Ruby on Rails favors convention over configuration (what does it mean? less crap more productivity). Now it seems Microsoft has realised this and they have come up with something that could counter people moving to ruby on rails by providing something that ruby on rails provide i.e. MVC framework to develop the application. I would keep on watching this (some sort of ) contest now with interest. Frankly, I myself recently downloaded ruby on rails to develop an application over the weekend to quickly implement my idea rather than starting development from scratch in asp.net. Now with this MVC thing ASP.Net is getting my attention again for RAD and I suspect there may be something more in pipeline from Microsoft. Stay tuned!
Resources:
(3 nice videos on ruby on rails to give you a quick overview)
plus another video tutorial