How to create a .mov video using iMovie 9 (the latest version).

1. In iMove, choose the "Share" menu
2. Choose "Export using QuickTime ..."
3. Name your file (please don't use spaces or special characters)
4. At the bottom, there are two "pop-up" menus.
Export: Choose "Movie to Quicktime Movie"
Use: Choose "Broadband- Medium"

5. Click "Save"

Now here's more information than you need, so ignore the rest if you like. If you use the above approach, this is the set of settings you'll have:

Video
Compressor: H.264
Quality: High
Frame rate 15
Key frame rate: 75
Bitrate: 220 Kbit/sec
Frame reordering: yes
Encoding mode: multi-pass
Dimensions 320 x 240

Audio
Format: AAC
Sample Rate 32,000 kHz
(recommended)
Channels: Stereo (L,R)
Bit rate 80 kbps

This gives you a sense of a nice set of settings for TTSB videos.