If you're interested in using OpenSolaris in the cloud, you can currently do so using Amazon's EC2 service. There are a bunch of machine images available. Most currently require registration (which has a quick turn-around), however, 2 are public.
If you're new to Amazon EC2, their Getting Started Guide is excellent. I would suggest working through the steps with the getting started machine image, and if everything works, try it again with the OpenSolaris image (ami-7db75014 for the US and ami-6c1c3418 for Europe). There's also a Getting Started Guide for OpenSolaris on Amazon EC2 that you may find helpful.
Another tool I've found useful is the Firefox plugin, ElasticFox.
From ElasticFox you can find AMIs, launch AMIs and open a terminal to connect to the instance. The first time I tried to connect to the instance I got the message:
Warning: Identity file /export/home/bleonard/ec2-keys/id_gsg-keypair does not exist.
After I created the ec2-keys directory and put a copy of my keypair file named id_gsg_keypair, it was able to connect successfully.