Adobe Marketplace and Exchange
"A beautiful looking site with a ton of free content submitted by Adobe users around the world. Their site makes it easy to find styles, projects, brushes, and shapes!"
AEProjects.com offers some really cool free presets and some you have to pay for
"A blog of presets and projects from designer Chris Zwar that are free to download and use. Some examples include a crosshair, spirograph, and image grids"
Video Copilot is one of the best kept secrets on the internet for After Effects tutorials they also offer a ton of presets and they're all free