Ballot initiatives and referenda are issues put on a ballot that voters may vote on directly. Most are part of the everyday business of local and state governments, for example millage increases or changes to local ordinances; while others address more dramatic issues, such as abortion, right-to-die statutes and, lately, marriage and homosexuality.
Initiatives and referenda are the purest form of direct democracy, and for that reason, once voted up or down, ballot initiatives are typically beyond the reach of state legislatures to alter or overule. They stand unless found unconstitutional in state courts, or until overturned by another initiative. Some find that laudatory; others believe that referenda can be abused. No matter who is right, and whatever the issue, referenda are important, and the wise citizen doesn't ignore them.

Ballot Initiative Strategy Center
Frankly liberal/progressive, it nonetheless provides a list of initiatives and referenda around the nation, as well as links to both pro and con web sites where available.
Initiative and Referendum Institute
Tracks ballots and initiatives nationwide.