I just need a book for an intermediate/advanced database developer in MySQL and SQL Server to start learning Postgres. Any recommendations?
I learned from the Postgres documentation. Its actually pretty good. Check it out: http://www.postgresql.org/docs/current/interactive/index.html
Its a great site to look at while you're working too. It always in my bookmark toolbar.
Aside from the documentation (which is excellent and fully recommended), I noticed that Amazon has a book that's being released this month (feb. 10'). I'm linking this one because while there's a bunch of other books in print that are good, quite a few were published in 2006 or earlier. There have been numerous new releases since then, so you won't be introduced to a lot of new features.
In any case, once the book comes out, remember to try before you buy.
I've learned a lot on Postgresql by following the planet: http://www.planetpostgresql.org. Particularly interesting are the description of the latest features on http://www.depesz.com. Mailing lists archives on http://archives.postgresql.org are also a goldmine.