What are you after?
1) Its all working OK, need to keep it that way
2) Its all working OK, but some parts are slow and need optimising and/or we need a few more reports / queries
3) Its broken and/or changes are needed, got to figure out how it fits together
4) Something else?
make sure the backups are sound. Get the most recent FULL backup, and restore it on a different machine (a PC will do, but you;'ll obviously have to install SQL, and patch to same version as the Production server).
DBCC CHECKDB ('MyDatabase') WITH NO_INFOMSGS
which will prove that there are no corruptions in the database - and also that your backup files can be restored.
Make sure backup files are getting stored to tape and offsite etc.
I would recommend getting some baseline performance figures, then if you make changes for any reason you will know whether you have slowed anything down (if they were not performance improvements) or speeded things up (if they were!)
Check on space requirements - so you can record the database file sizes, over time, and see if you are imminently going to run out of disk space
Consider an upgrade to SQL 2008. No point if the database is static, because you'll have to test that everything still works (regression test) but if you need to make any changes you will have better tools, features, and disaster recovery opportunities under SQL 2008.