Support for bulk reads/writes ?

I have looked around quite a bit and could not find any information on
whether or not Postgres supports Oracle-style array usage for bulk
reading/writing of the database, e.g. bulk insert statements ?

I have a web application --- I'm acquiring/calculating various data
throughout a user's session that needs to be written to the database. I
could either just insert/update the data in Postgres as it is computed
throughout the session, or, I could keep the data in memory (using servlets,
storing the data at session scope) and then write it all to Postgres when
the session ends, if there were any advantage to doing so, i.e., if there
were a way that I could insert the data in bulk to save a bunch of trips
back and forth to the database. Otherwise, there would seem to be no
performance difference in whether the web app is executing a bunch of SQL 
statements over the course of the session vs. executing all the same 
statements at the end of the session.

The web application could experience high loads, in terms of the
number of simultaneous user sessions, which is why I'm concerned about
performance.

thanks,
charlie