Hardware

As only the Mac Pro has the ability to take an internal capture card, video capture options for Mac users are more limited.

The top options would be the Elgato Video Capture for composite video, or the Intensity by Black Magic Design which accepts composite, component, or HDMI video (though it cannot decrypt streams using HDCP).

Elgato Video Capture

(Elgato users can explain their experiences here)

Intensity

Intensity users will likely capture their streams using Black Magic Media Express. This software comes with the Intensity, and supports Quicktime codecs. However by default it will only offer uncompressed video for maximum-quality recording. This is not optimal for space or disk performance, and so it is a good idea to install the ProRes codecs (using unpkg if necessary to get to the individual codecs) in order to have more options. Quoth CMiller:

There are several variations of Prores:

Prores 4444- Used primarily for 4K work or feature film finishing.
Prores 422 (HQ) - High quality used for HD finishing. Same as 422 but with higher datarate.
Prores 422 - Used for HD editing. broadcast quality.
Prores 422 LT - 2/3 the datarate of 422. Used for proxy work mostly.
Prores 422 (proxy) - 1/3 the datarate of 422. used for proxy work.

Capturing in 422 (HQ) and 422 both work wonderfully for 720p capture.

Software

Capturing

The software used for capturing can vary with the capture hardware used. See above.

Quicktime Broadcaster is capable of recording from a video source, additionally.

Editing

On the software side you will need only iMovie (free if you know how to get it, i.e. with a new Mac). From here it's pretty easy - just import whatever you want, then edit your clips so they start and end when you want them to.

(TODO: verify the following two paragraphs. I suspect a workflow of iMovie to Handbrake is more useful. Verify this.)

Once you have your clips ready to go, export them one at a time. If you want to, you can end your capturing adventures here by exporting to MPEG-4, the highest quality Internet-friendly format offered with QuickTime (choose "Expert Settings" when you go to Share your movie). I'd use 512 Kbps for the video track and 64 Kbps for the audio track. All of the encoders should be set on "Better" quality. Also make sure that "Hinting" is turned off. This will create a file that takes up about 4.3 MB for every minute of video it contains. Feel free to play around with the two bitrates to find a level of quality you feel is satisfactory.

If you want to create a 60 FPS file (double the framerate you will create by using MPEG-4), you will need to export your clips as full quality AVI files, using the either NTSC or PAL DV codec (not DVCPRO). By installing the MainConcept DV codec on an available Windows PC, you can use VirtualDub (which, for some reason, only runs under Windows at this time) to make full framerate videos out of your clips, even though you didn't capture them using VirtualDub. For more about this, please see the EDITING VIDEO section under the Editing in VirtualDub page.

Streaming while Recording

As streaming is so popular in the speed running community now, a note on streaming is useful. Quicktime Broadcaster is a great option for Mac users to broadcast a stream, though some use Adobe's FMLE. These tools can record while streaming.

These tools are great for a very basic stream direct from a video source, but for fancier stream effects, CamTwist is a great option. An alternate tool like Blackmagic Media Express can be used to record the direct game feed, while CamTwist can capture the part of the screen featuring that feed, and then broadcast it with additional features, such as splits, live camera, text, and images.