Disk is full, what's cool to get rid of?

Hello, quick question.  I've run into an issue with the disk that my 
development box is on filling up and preventing pretty much any writing 
(inserts, updates, deletes, etc...) from happening.  Other than some 
piddly text logs the db is pretty much the only thing on the box.  So, 
my question is:  what can I do to free space and run a full vacuum? (I 
was not the one who set up this box and there has been virtually no 
administration or maintenance on it that I know of...)  How about the 
WAL files in pg_xlog?  How critical are they when no data on the system 
is critical in and of itself?  Any suggestions would be greatly 
appreciated...

-- 
erik jones <erik@myemma.com>
software development
emma(r)