Due to legal demands, the site was forced to remove the MLB, NBA, NCAA, NFL, and NHL vector collections on November 12, 2008.
The best way to find vectors is to do a search for team media guides in PDF format. Many sports teams offer their media guides in PDF format and, quite frequently, these PDF media guides contain embedded vectors. You can open and edit PDF files much like any other vector file with programs such as Adobe Illustrator. Note that most older logos no longer in use since the mid-1990's will likely be impossible to find in vector format.
You may request vectors via email. To make your requests navigate to the Contact page and click on the email contact image. Most requests will be handled within the hour.
If you are unable to find a vector you can have one made for as little as $6.00 per vector from one of the two vector creation sites listed above. My personal favorite is 7Vector. Their work is outstanding and requests are always handled in less than 24 hours.