Go to 3rd Party Apps sections and OTA Apps thread at the top. Theres TalkLock and stuff like that. I dont use any of them but people say they work.
Link for TalkLock
For a free app this one works really well. It automatically starts up after like 3 secs and if you want to unlock just slide thumb across the screen and then you can re-lock it by pressing the menu button and and select lock screen again. Saved a bunch of muted calls!
Wow... searsh the threads before you post. I'm suprised you didn't get slammed yet. Maybe the forums are taking a turn toward friendliness! StormLock, TalkLock, Screenlock...all work fairly well from what I hear. ScreenLock is free though, the StormLock isn't, I dunno about TalkLock.
I wouldn't recommend TalkLock, sometimes either it stops working or my cheek accidentally unlocks it. Also, it is always running in the background(hold down the bb menu button and you will see it running), which uses up app memory, and on the Storm we need all the app memory we can get! I really like ScreenLock though, as it doesn't run in the background, and you don't pull a bar to unlock, you have to physically hit the Back button.
To re lock it, you have to press the BB menu key and then hit re lock. Its way better, imo! Here's the link:ScreenLock for Blackberry Storm