I just found this Color Contrast Checker web site on del.ic.ious. You just give it your foreground (text) color and background color, and it will tell you if there is enough color contrast "when viewed by someone having color deficits or when viewed on a black and white screen" (W3C).

The tool will indicate that the colours pass the test if both the colour difference and the brightness difference exceed their threshold. It will indicate that it sort of passes if only one of the two values exceed their threshold. And finally, it'll fail to pass if neither value exceeds its threshold.

I have seen enough hard to read web pages (even by very skilled programmers) that I thought it would be worth while to post this.