Media Converter is a free online program that allows you to save clips from the web. Very handy to have to save that hard to find clip or if you don't have internet access.
I have used InfinteLooper for looping a video. I was showing a clip of a figure scatter doing a pirouette in my physics class. The clip was only a few seconds long and wanted to talk about her speed of the spin and her arms. I found having it looping on the board as they walked in or as I was talking a great help rather than going back and always hitting the play button again. This too gave students the opportunity to look at it over and over and to come to an understanding in their own time. It also was great for me as I could really focus on facilitating the discussion and extracting students knowledge.
These are only two I have used a lot so far, I am sure there are plenty more out there... Enjoy!