This Greasemonkey script is great for South African youtube users with 192 or 384 kbps “broadband” ADSL as it makes everyone’s favourite video site autobuffer the videos! You can also set it to playback all videos in HD and hide in-video advertisements.
From the description:
Buffers the video without autoplaying, removes in-video ads, and puts it in hd if the option is on
To use Youtube Auto Buffer you need Firefox with Greasemonkey.
YouTube Auto Buffer & Auto HD & Remove Ads
Edit: A similar, maybe even better script: YouTube HD Ultimate
