The above image shows the lines without pressure and with pressure. I'm newbie, and looks like my photoshop CS3 don't have the "without pressure" option. Follows a printscreen of the brushes options:
Any idea how to enable the "with pressure" line? Does it exist in Photoshop CS3?
If you go just a bit deeper into these options you can find different things you can do and some of them have drop down list which has few other options including "Pen Pressure" which of course works mainly if you have Drawing tablet.
Shape Dynamics - Controlling: Size, Angle and Roundness by pen pressure can be found here.
Other Dynamics - Controlling: Opacity and Flow Jitter can be found here.