The Stopmotion software for stop motion animation is included in the distribution of UbuntuStudio. The demo here was done with UbuntuStudio 8.04 based on Intrepid.
I used an A4Tech web cam which is v4l2. Stopmotion has a problem with these kind of web cameras so you'll need to follow Aearenda's solution here: http://ubuntuforums.org/showthread.php?t=931208 . I do hope they've already solved this in Ubuntu Jaunty 9.04.
Create an mplayer video import device in Stopmotion
Start Stopmotion and in the menu find settings->configure stopmotion or ctrl-P.
Click add button.
Resize the dialog box to see the start deamon & stop deamon text boxes.
Click video import tab.
In the start deamon text box enter the following (change the ~/RENDER/stopmotion/ folder with your preference):
~/RENDER/stopmotion/startmplayer $VIDEODEVICE $IMAGEFILE 2 0.25s .tempjpgs &
In the stop deamon text box enter this code:
killall startmplayer && killall mplayer
Download my startmplayer file from: http://www.mediafire.com/file/zm2ytmnqa2j/startmplayer.zip.
Extract this startmplayer file in the ~/RENDER/stopmotion/ folder, you can change this folder.
Then follow this demo:
Finished product (a bit crude):