Fortunately, there are some amazing resources out there. The pgsql-general e-mail list has oodles of helpful people, and great questions (and answers!). Get it in digest format, or prepare to have your inbox inundated with PostgreSQL goodness. But I've learned a ton just from reading messages on that list.
There are some great PostgreSQL-related blogs, as well. Many are on the "Planet PostgreSQL" aggregator, at http://planet.postgresql.org/ . Between those blogs and the e-mail list, you'll have lots of good stuff to read.
Finally, Packt published two books about PostgreSQL 9.x in the last year, both of which are excellent. One is an administrative cookbook, and the other is a high-performance guide. Definitely worth reading (and re-reading).
I'm in Israel, where MySQL is the open-source database king, and where people have barely heard of PostgreSQL. But I get about a call a month from someone who needs help with their PostgreSQL usage or configuration, and besides the nice feeling of having become the local go-to guy on the subject, it's also fascinating for me to see just how many serious places are using PostgreSQL -- but under the radar, without fanfare. They know that it's a great database, but no one else knows that they know.