Some of the companies that fit this parameter include RightScale (founded by Thorsten von Eicken, a cofounder of former portfolio company GoToMyPC) and one that I am looking at in the email archiving and compliance space which has a number of OEM partners reselling its service. Rightscale is an on-ramp to Amazon EC2 and other clouds and provides automate systems management. It kind of reminds me of a next generation Tivoli or Openview. The beauty is that the whole sales cycle is quite frictionless and all web-based which means an oppotunity to scale quickly. 

There are a number of other recent players I have seen including one for BI in the cloud (not exactly sure what the killer app here is yet) and many others. Of course the trick here is not to get enamored with the word "cloud" but to really understand the business problem that is being solved and why leveraging a cloud computing platform offers better economics, scale, and competitive advantages. 

As I dig deeper into some of these companies, it is clear to me that software purpose-built from the ground up to live in a cloud has a huge advantage since it is hard to retrofit off-the-shelf software to leverage all of the benefits offered by Amazon, Rackspace, and the like. Secondly, many of the better companies have built some slick tools and services to solve difficult problems like how to make customers feel like they have their own privated, dedicated systems while still keeping costs low.  Finally, from a go-to-market perspective, a number of the companies I have spoken with have not gotten the question of whether or not they could scale as they quickly point to their backend provider and move to the next objection. So, if you have an application targeted at the SMB market that is taking advantage of cloud economics, please feel free to contact me.