Apple has released iMovie Plug-in Pack 2.1.1 for Mac OS X.
The collection of effects, transitions and titles is available for download from the company's Web site. It's solely for Mac OS X, and is a 480K file.
The effects include: Flash; Ghost Trails; Mirror; Mirror Advanced; and N-Square.
Transitions include: Circle Closing; Circle Opening; Radial; Warp In; Warp Out; Wash In; Wash Out.
Titles in the pack include: Subtitle; Subtitle Multiple; Zoom and Zoom Multiple.