Color Logo Maker is a simple graphics tool that will quickly create Google-style colour-cycling logos.
To get started, simply enter the text you'd like to use in your logo, and click the Generate button to see how it looks. This may quickly highlight one weakness of the program, in that you can't adjust the logo size: if you enter too many letters then it simply won't fit. Try adjusting the font and font size to see if that helps.
Assuming your logo fits well, though, you can then customise it by choosing the colour sequence for each letter, along with the shadow and "text bump" details that give your logo a 3D look. Again, just enter whatever figure you like and click Generate for a preview; if you get lost, clicking Reset Settings will restore the default values.
And once you're happy, click Save to save your logo as a BMP, PNG or JPG file.