modbot is a utility to queue videos to be played, with a list of approved videos that will automatically play when requested. Below is a list of supported commands.

CommandDescription
!request <link/searchterm>request a video to be played
!queueget the number of songs in queue and which (if any) need to be approved
!queue <position>get information about the video in the given position in the queue
!wrongrequestundo the last request you made
!requestedbysee who requested the current video
!modstatsget a percentage of how often there are mods in the channel (aside from modbot)
!syncvidsynchronize video position (or see a video that was started while having youtube videos disabled in the flash client)
!nowplayingget the title (and link) of the currently playing video
Mod commands:
!playnextplay the next video in queue without approving it (to see if it's ok)
!approvemark the currently playing video as good, or if none is playing the next in queue
!approve <link/searchterm>mark the specified video as okay
!approve nextmark the next not yet approved video as okay
!approve entire queueapprove all videos in queue (for playlists)
!badvidstop playing the current video and mark it as bad
!badvid <link/searchterm>mark the specified video as bad, preventing it from ever being queued again
!skip <number>skip a given number of videos from the queue without approving them nor marking them as bad, if no number is given it defaults to 1

You can also just play videos manually/the good old way and they will be marked as good.