In many states, such as California and Washington, voter approved initiatives are commonplace. There is now a searchable database of these voter approved initiatives which allows researchers to sort by state, subject matter, form of law, ballot number (where available) and year. For example, anyone tracking education initiatives across the states can now easily retrieve this information with the Miller-Rose Institute Initiatives Database. The site claims that this database provides information on all statewide initiatives adopted by voters in the United States from 1904 through 2010.
An additional feature of the Miller-Rose project is that it contains post-election challenges to these initiatives, identifying court cases by case name and citation, legal basis for the challenge, and outcome.