There is a [built-in system](http://mathoverflow.net/tags/synonyms) to automatically create tag synonyms by the nomination and voting of high-reputation users.  Unfortunately, it appears that hardly anyone ever looks at this page (and the qualifications for voting are fairly demanding), so I'm posting it here to try to get it more attention.  In particular, all of the synonyms marked as "pending" are languishing in neglect until they get four people (or a moderator?) to vote for them, though I think some of them are going the wrong direction.