The "You must be logged in to do that. Log in (or create an account real fast) and we'll send you on your way." text is almost unreadable for me (Opera?). Thin red monospace font on big fat red background.

Good job on making your frontpage usable without Javascript (probably a SEO thing, heh). It is not very beautiful but all information is accessable.

Maybe show some examples of what one gets from the Voltmeter? Why would I give away my mail address for something I don't know much about. I too find the "Run Voltmeter" -> "Oh nonono, you have to signup!" questionable.