YouTube to iMovie Converter can convert Youtube video files (*.flv) into MP4 so that they can be opened in iMovie. It can also import AVI, MOD, TOD, MPEG, WMV, VOB, 3gp, 3g2, MKV, MTS, m2ts, TP, TS, DV, DAT, etc.
Information regarding Project Releases and Project Resources. Note that the information here is a quote from Freecode.com page, and the downloads themselves may not be hosted on OSDN.