If there's one bothersome side effect of getting a long Web video sent to you, it's getting to the good parts. In some cases, the part your friend wanted you to see could be a few minutes in, and you might not have the time (or patience) to sit through the rest. A service called Splicd fixes this, by letting anyone drop in a YouTube video URL, then pick the start and end point.
It's not a very pretty implementation, but it works. You've got to manually plug in the start and end times, which requires skipping around to the part you want in YouTube, then heading back to Splicd. Once it's worked it through, you get a permalinked page that you can share with friends.
What's nice about this system is that it doesn't require extra time to re-encode the video; when you've put in those changes it's instantaneous. The downside to that is that the finished product cannot be shared outside of Splicd's site.
I expect that YouTube will eventually offer such a feature in its own player. Competitor Viddler has offered it for some time now, and with that system you can control those times on embeds, too.