Lies, lies everywhere... I use Vegas and After Effects.
As for free alternatives, http://nightcoreuniverse.net/viewtopic.php?f=15&t=5380
this seems like a pretty simple and effective program.
Oh, and render audio at 44.1kHz, not 48kHz as Russen said. All music is in 44.1 and will be corrupted by YouTube if you try to convert it to 48.