Microsoft Connect (blog, twitter) is a site where you can post feedback to improve the quality of many Microsoft products and impact the direction of those products. As of this writing, the site accepts bugs for 51 products and suggestions for 34 products, all from the community. You will need a Microsoft Live ID to submit a bug or suggestion.
The site has a nice dashboard where you can view feedback you have selected to watch, feedback you have submitted, and feedback you have participated in. Each line in the dashboard shows the number of comments, the number of workarounds, and the status.
On many occasions I have run into a bug with SQL Server, and have used connect to see if someone else has notified Microsoft of the bug. And many times Microsoft or another community member will have posted a work around. I have also posted suggestions for SQL Server, along with many others, and have seen those suggestions implemented. So if you find a bug, or have an idea to improve a Microsoft product, check out Microsoft Connect.