Many people are using a trick to view any YouTube video in high-quality -- simply append &fmt=18 to the end of the URL. This is a job for AppleScript! Here are two simple versions; the first, for for OmniWeb:
tell application "OmniWeb"
set current_url to the address of active tab of browser 1
set current_url to current_url & "&fmt=18"
set the address of active tab of browser 1 to current_url
end tell
...and the second, for Safari:
tell application "Safari"
set current_url to the URL of current tab of window 1
set current_url to current_url & "&fmt=18"
set URL of current tab of window 1 to current_url
end tell
These can be placed in ~/Library » Scripts » Applications » AppName for easy access via the Script menu.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20080316111042524