Vote Smart remains completely non-partisan, and they prove it in three ways: 1. They never accepting funding from special interest groups, corporations, or the government, and are totally dependent on small individual contributions and foundation grants. 2. Any member of their board with a political history must join with a political opposite, which has included such "odd couples" as former Presidents Carter and Ford, and Michael Dukakis and Bill Frist. 3. They operate a lot like the Peace Corps where 90% of the work is done by trained, supervised student interns and volunteers who come year-round to their headquarters in southwest Montana at the Great Divide Ranch.

I'd also add that the bulk of the information they provide at votesmart.org, for example a candidate's voting record, a transcript of their last television appearance, or their campaign financing information, doesn't provide any opportunity for slant or bias. They are essentially putting this info all in one place.