Search the market for 'screen mode widget'. There are three settings for it, regular - lock/swipe ('sleep auto'), bypass the lock ('awake stay') or always on ('screen stay'). You want it set for 'awake stay', it works really well. You can turn the screen on w/the power button, camera key or volume rockers when it's set to 'awake stay'.

 

ScreenModeWidget v1.4 Application for Android | Tools

 

Screen mode widget is great but even if you slightly press the camera button (which is very sensitive) you'll end up unlocking your phone. If you're got a pattern lock, you might wanna check out "autolock"
You'll be able to set up a time of delay before your phone goes into the pattern lock mode after your screen turns off. You'll have to pay for it but if it's something that frustrates you, I believe it's worth the money. Besides, we wouldn't think twice about spending the money if it was a tangible item we'd want to try/eat.

 

Also try out myLock, which unlike screen mode will keep the vol and camera keys locked. We have a lite version accessed with a widget toggle, or a complete version which has several useful features one of which is a keep screen awake checkbox.

myLock for android

 

I just found one called Lock Delay, it works perfectly. Some other ones end up making you both slide to unlock and do the pattern. This one does exactly what it's supposed to... delays your lockscreen for a set amount of time after you press the power button on your phone. It's very configurable also... if you don't use a pattern, you can just use it to delay the slide screen, or you can tell it not to have a slide screen when you press the power button.

 

SMW its great.
Ive been using it for four days.

 

+1 for MyLock! check this article out:

MyLock Is an Alternative Lock Tool for Android Phones

 

The is also Keyguard Disabler on the market. Much more dependable than SMW, but without the "Screen Stay" option.