Backups of course.
Apart from that it depends on how reliable it has to be and how much performance you need. As long as you don't have special requirements on reliability and do not get very many hits it will run fine. It does automatic maintenance (auto vacuum) like removing dead tuples and analysing data to update the statistics used by the query planner.
However when the load rises you might have to tweak the parameters controlling auto vacuum. Also when performance drops you will have to start tweaking other parameters and monitor performance.
Personally I found the following book very informative PostgreSQL 9.0 High Performance. It discusses things like which hardware to get, which filesystem to use and how to tune postgresql it self.