The list of Project Management software in the market is long but they are some we really like and can recommend:
1. Basecamphq.com - we have been using this tool since 2005 (we were an early adopter) and have had an unlimited account which has paid good dividend. We use other tools too but this tool is unrivalled for its ease of use and simplicity. There is no learning curve and it does what a PM tool needs to do. Check out their plans at http://www.basecamphq.com/signup
2. Pelotonics.com - we had a role in building pelotonics and feel proud of this. The tool is essentially basecamp on steroids. You can sign up for pelotonics at http://www.pelotonics.com/signup_new.aspx (I really like the evernote integration).
3. pbwiki - if you are looking more for a wiki layout consider this. Very generous packages and great design make this into a great tool. http://pbwiki.com/buynow.php
Some other tools you can consider:
http://www.huddle.net/
http://www.wrike.com/
http://www.jivesoftware.com/