Before you go and harm your databases with this, please take a read through this - Managing Transaction Logs[/url]
I'm going to guess you have no log backups and hence the log grows large. If so, the fix isn't a temporary switch to simple recovery and a shrink, it's scheduling log backups.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability