How to speed up video footage to make a timelapse video?

Avidemux

(has GUI for both GTK and QT). (see Video->Frame Rate in application menu)

You could also try Virtualdub

Sorry for that last comment it was the wrong link. Also take a look at this to see if it helps.

Just use ffmpeg - GUI programs always get outdated almost instantly

ffmpeg -i [input video] -filter:v "setpts=[RATIO]*PTS" [output video]

Here you have to replace [RATIO] with the number you get by dividing the duration (in seconds) of the output video with the duration of the input video. So if your traffic video original file is named traffic.webm and you want to name your output traffic-timelapse.webm the command would be (note that 30/(60*60) = 0.0008333 ):

ffmpeg -i traffic.webm -filter:v "setpts=0.0008333*PTS" traffic-timelapse.webm

Kdenlive also has a video speed effect.

You could use slowmoVideo for the purpose. The description of the software from their site:

"slowmoVideo is an OpenSource program that creates slow-motion videos from your footage. But it does not simply make your videos play at 0.01× speed. You can smoothly slow down and speed up your footage, optionally with motion blur."

You can find the latest Ubuntu build of this application at:
http://slowmovideo.granjow.net/builds.php