Most of the major urban counties in Colorado (and many that are not) have moved from a precinct based, in person voting system to either mail in ballots or vote centers. A mail in ballot is pretty self-explanatory. In a vote center system, a number of voting centers are set up throughout the county, and you may vote at any of them, regardless of where you may happen to live. Denver and El Paso County (home to Colorado Springs) are the biggest counties still using the traditional system, and that may not last.
Both approaches increase voter turnout, because mail in balloting and greater choice of a voting location can be convenient, and reduce the chances that a voter will cast an invalid ballot because they can no longer accidentally appear at the wrong precinct. In the automobile age, being able to walk to your local precinct is both not reality in the suburbs, and not something that people are inclined to do even when the polling place is close. Skilled election judges and accessable locations willing to host elections are also continuing to grow scarce.
The ultimate realization of this, of course, would be to go from a county based vote center system to a state level voter center system. The basics of this approach are already in the works as the state develops a central statewide voter registration database, both to reduce fraud and to ease the voter registation process. A statewide vote center system could easily dovetail with this database.