I have 1GB databases that grow several GB log files. How do you safely clear those logs? Well, probably the best practice includes backing them up. That was overkill for me, and sifting through all the documentation and forums (eventually) led me to this simple pair of statements that do the trick immediately:
backup log [dbname] with truncate_only go DBCC SHRINKDATABASE ([dbname], 10, TRUNCATEONLY) go
Update: Mathias added a comment that deserves calling out:
Warning: Clearing the transaction log with TRUNCATE_ONLY will break your backup chain needed for FULL recovery. A FULL database backup should be executes right after truncating the logs. More info.