In spite of a slow start at its release, the G1 now has several usable video players. There are three: Meridian Video Player, PlaysVideo, and Video Player. I recommend Meridian because I found it to be the most responsive and I like the screen gestures and the one-touch pause. Marketplace users rated it a 2.5 out of 5, but the turnoff could easily have been the very unpolished interface and the very grammatically incorrect tutorial that comes up when you start the player the first time. Both of which won't matter once you start the movie. The comments were generally not informative, although some did say the player doesn't save your place when you're interrupted by a phone call or shut down the device. This is a must-have feature, but it will also be very simple for the developer to fix in a future release. (I also found that none of the others save your place either.)
The first step is to download Handbrake. This is a snappy, simple, free video converter that also has a quick preloaded format for the G1. You'll also need DVD43 if the DVD is encrypted (and you own the disc).
Install Handbrake and DVD43. Put your, completely legal, DVD into your drive. Open Handbrake and click... yes, that's right, "iPhone & iPod Touch" in the presets bar. You've now stepped into a gigantic Tyrannosaurus Rex footprint left by the iPhone. Thanks, iPhone. You've clearly marked the way.
Next, click "Source" in the upper right hand corner. Choose your DVD drive. Pick the title that looks "right." For a feature-length film, you should pick the longest one, the one that's about two hours long. In the case of a set of TV shows, you should pick the medium length titles one by one.
Then click "Browse" next to the Destination textbox (about halfway down) to choose a destination file. This should start out on your hard drive and then you'll move it to a directory called "Video" at the top level of your SD card.
I recommend changing the format to MP4 because the encoding is faster and I ran into a mysterious 30 minute limit using M4V. The codec, by the way, is called H.264, but you don't need to select it. It's default on the next tab. It is a very modern algorithm with good compression and high quality. The video won't come out looking like something on youtube.
Type "320" into the height box and hit "Start." This will create a video that will fit nicely to the edges of the G1 screen. When the encoding is done, move the file to the Video directory on the phone.
Pop open your video player and enjoy!
Note: I am not responsible for the copious amount of time that you may spend ripping DVDs. Unless you have a very fast computer, it will take about the same amount of time to rip it as watch it. You don't have to babysit the process, of course, but it's still prohibitive to casual use — highly recommended for waiting rooms and airports.
Update: Meridian now saves your place.