MPEG-1
TMPGEnc - [rating: C+] [free for mpeg1] [ver/tst: 2.52.34.129] [win] - MPEG-1 files. Cut off the beginning or end. Join multiple files. Cut segments and merge. The MPEG1 tools are free. Sometimes there are audio video sync problems, however, there are some workarounds that often clear up the problems. In TMPGEnc menu choose FILE, MPEG Tools, and click on the Merge & Cut tab.
MPEG-2
TMPGEnc - [rating: D-] [trialware for mpeg2] [ver/tst: 2.52.34.129] [win] - MPEG-2 VBR and MPEG-2 SuperVCD Files. Cut off the beginning or end. Join multiple files. Cut segments and merge. The MPEG-2 functionality of TMPGenc is "trialware" only. Also, TMPGenc cannot seem to keep the audio synchronized with the video.
Mpg2Cut2 - [rating: A] [free GPL] [ver/tst: 2.8.6d] - cuts and merges by groups of frames, mark the "FROM" and "TO" points of the clip that you want to keep, and then save that selection to a new file. Tested with MPEG2 file created by ADS Instant DVD and success, no audio video sync problems, no quality loss (does not transcode / re-encode). homepage
AviDemux - [rating: ?] [free] [win nix] - homepage
VideoReDo - [rating: ?] [payware $95.99] - homepage
XviD (avi)
H.264 (mp4)