I'm a heavy user of the IconFactory's xScope, a great universal tool for designers which we've covered several times. For those of us with a need for it, it's worth every cent. I happened upon a freeware application today, though, which provides a subset of xScope's very useful features: omnidea Rulers.

This free app does a great job of providing on-screen guides, allowing the insertion of horizontal, vertical and intersection rules. It also gives you Photoshop-style rulers at the top and side of your screen for positioning. A HUD provides mouse coordinates and a magnifying glass, with two minimal views and one that shows all of the data at once.

Rulers provides screenshot capabilities. More useful than that, though, it also has an auto-measure tool similar to xScope's "Dimensions" mode. This is infinitely useful for quickly determining the pixel size of any on-screen area of which it can discern the edges. When Rulers is in the foreground, pressing Command-A will instantly show cross-hairs and a measurement for the area surrounding the mouse cursor.

Rulers is pretty darn useful, especially for web designers, and it's free. Pick up a copy from omnidea and enjoy.