Do you have any preference as to whether the CMS is written in PHP or ASP?
For ASP solutions I love SOOP Portal
, which is completely free and fanatically supported and modded by it's user community. I used this for quite some time, and was very happy with it. I ultimately opted for a PHP based solution because it is my preference to do my development work in PHP, and also PHP/MySQL hosting in general is cheaper than ASP/SQL.
I tried Joomla
recently, and it is very nice, but it wasn't really what I was looking for personally, and I ended up using e107
which I am very happy with.
At any rate, you can find a lot of information on CMS in general here