I don't know if this is common knowledge and I'm just late to the party again but I found a neat little Firefox extension called VideoDownloader that basically does what it says on the tin. After you've installed it, it places a small icon in the bottom right bar of the browser window that you just click on while a video is loading on almost any video hosting site (google, youtube etc) and another window will open up with a button for you to right click on and save the file where you want it. Up until this point it works on mac and PC. You might have to alter the file extension but there's tutorials on the site.
Once you've downloaded the file there's also a free way of converting them to a more useable format. A lot of them are saved as .flv files that will need a certain kind of codec or software to play. If you download Super you can convert them to any other format.
I often find that I want to watch a video more than once and this way you can download the whole thing, wait until it's down and watch it as many times as you want and no streaming pauses too.
You can get the Firefox extension here.
Click.There's a link to help and tutorials at the top of that page.
And you can download Super video converter free here (PC only).
Click.When you try to download Super it's not very obvious where to click to get the actual file. If you scroll to the very bottom of the page you will see a few "Ads by google" text links, just below that it says Download Super © click on that link and it will take you to another page, at the bottom of this page there's a few Download Now buttons. Click one and wait, I only got 10k/s download but it's a good free bit of software.
Hope that makes sense
Mark