Is there any way, aside from looking at the rulers and measuring by eyesight, to find the precise distance between one guide line and another?
Use the Ruler Tool. Click and drag from one guide to the other then look at the Control Bar. The "L1" item will be the length of the measurement. Or use Window > Measurement Log and click the "Record Measurement" after dragging. It will display all the measurement information.
Even Quicker way to measure distance between two guides is to use the marquee tool. If you are on photoshop CS6 - Create a Marquee rectangle snapping from one point to the another. CS6 shows a tooltip with Width and height while u create the box. If on lower than CS6, you would get the values in the info Dialog - (CMD + fn + F8) or (Ctrl + F8)
Marque tool will give x/y distances in info pane and you can just keystroke 'm' to get to it. Also if measuring guides or sizes it can be set to snap to bounds, etc.