I have a job that goes through and deletes all workcenter messages older than 30 days - its a pretty easy job to create - just base it on the R01131P and modify it to delete all records where date<{system date}-30 !
Workcenter messages over time are freakin' HUGE if not purged often.
Another little niblet is - if you're running invoices - I would also check the F42565. This should be empty, but if you had a couple of runaway invoice jobs that you had to cancel - you should truncate this temporary work file. Obviously make sure that you only delete records where UPMJ < todays date - just to make sure you don't delete active F42565 records !
DON'T delete OMW logs and DON'T delete F9312 (Security History). If you're a SOX compliant organization, you need ALL of those records - and if you ever do an upgrade, its very very important to know the history of an object.
Last but not least, there are some "purging" and "archiving" documents out there on the knowledge garden - I believe that Oracle has got the new "Knowledge Browser" working. There are some very cool presentations and documents out there that are application specific that will certainly help.