Wikipedia.org is a virtual treasure trove of vector graphics for just about any brand, organization or group. Take Major League Baseball for instance. The following is by no means a comprehensive list of all the current, or past Major League teams — it is presented here as a guide to get you started with finding your favourite team on Wikipedia which contains high-resolution scalable vector graphic logos and insignias for the team you are most interested in. SVG data can be converted into PSD, TIFF, EPS, Illustrator AI files, Freehand FH files, PNG and many other formats using many online services such as this one.
TL’DR: If you don’t own one of these teams it’s best you do not use these logos for any reason.
So what’s the point of telling you about these if you can’t use them? A cursory search across the web shows that many sites have had takedown notices for vector logos where it concerned teams from the NBA, NFL, MLB, NHL and others. They obviously don’t want you to have vector data of their team logos. However, there are also many sites out there selling the same logos or pointing to dubious links on cloud storage services.
The point is this, if you need vector content for any kind of corporate organization, open source Linux, software product, social network, or clip art then I strongly suggest you search Wikipedia first. So far I’ve been able to find anything that pops into my mind.
The best way to find content is to use Google with the following string:
wikipedia SVG item
Replace the word item with the thing you want to find. For example, Autodesk, Red Hat, Whitehouse etc.