There are many talented developers in the MusicBrainz community, and as a result, there are lots of ways to make the task of editing and expanding MusicBrainz data simpler and faster.
For adding releases
Userscripts generally only work under Firefox with the Greasemonkey extension. Google Chrome support can be very hit-or-miss, Opera compatibility is very sparse. Script compatibility under Google Chrome is greatly increased when using the TamperMonkey extension.
Bandcamp, Beatport, and Local File Parsers (with great assistance comes great responsibility)
These parsers are meant to be run at the command line passing in either a URL (Bandcamp release, or Beatport release), or a directory with a set of files. The local file parsers run on all files in a directory with the same extension, and are intended to output a whole release, suitable for copying / pasting into the tracklist page's Track Parser. They are written in Perl, require at least Perl v5.10 and a differing set of Perl Modules based off the particular service. The local file parsers are currently format specific.