FxFactory offers at least 14 free plug-ins with the trial install, and tutorials on their website, including CoverFlux (like iTunes CoverFlow) and Manifesto (a title roll generator). [UPDATE: Yanobox is now offering another free FxFactory filter, Barcodem. Idustrial Revolution has more in Freebie Pack 1 and elsewhere.]
CoreMelt FREE is 33 free plug-ins collected from CoreMelt (leaving 180 others for purchase). CoreMelt plug-ins no longer require FxFactory.
By the way, if you're on Windows an easy way to do the Cover Flow effect is with an After Effect project by Paul Tuersley. You just have to animate some sliders. See also a free project from Alex "dinners" and a tutorial by Mattrunks, Effet Coverflow 3D automatique sur After Effects, which includes the project in English.
Both packages are Mac-only FxPlug filters that should work in AE, Final Cut, FCE, and Motion. Here's the list of the CoreMelt FREE plug-ins and a sample tutorial movie for some of them:
Multipop Forward, Filmstrip, Carousel, Continuous Random Pan, Image Grid, Advanced Vignette, RGB Levels and Curves, Dewrinkler, Old TV, Blowout, Godrays, 3D Shatter, Analog Glitch, Soft Edge Wipe, Blend Mode Dissolve, Curl Apart, Exposure Flash, Projector Malfunction, Random Crop, Video screens 2way, 8 Band EQ, 16 Band EQ, 127 Band EQ, EQ Line Segments, EQ Simple 3D, EQ Pixelstix 3D, EQ Tower Cities, VU Analog, VU Digital, VU Rolling Gauge, VU Audio Radar, WV Oscilloscope, WV Voiceprint, WV Waveforms 3D.
For more free plug-ins see 55 Free After Effects Plugins from Filmmaker IQ (July 2010).