The SE chapter of the Colorado Renewable Energy Society (SECRES) provides this information as a guide for those who are considering investing in renewable energy for their residential or commercial building. Solar energy (as opposed to wind and other forms) is more commonly used on individual buildings as it is more easily deployed at smaller scale and in urban areas. Solar electric (photovoltaic or PV) systems convert sunlight to electricity while solar thermal systems convert sunlight to heat. Home Power Magazine provides very useful tutorials on Solar Electricity Basics and Solar Hot Water Basics.
While wind and hydro-electric power are most commonly deployed at very large scale for utilities, some individuals may find these technologies useful. Home Power Magazine has a tutorial on wind power and one on micro-hydro.
Financial incentives exist to help offset the cost of renewable energy systems. The Database of State Incentives for Renewables and Efficiency (DSIRE.org) provides up to date information on all federal, state and local incentives, both residential and commercial, for renewable energy and efficiency upgrades.
SECRES does not recommend specific renewable energy installers. However, there are lists available. The Colorado Solar Energy Industries Association (CoSEIA) provides a list of solar electric and hot water installers in the state. Look for an installer who has NABCEP certification. As with any building contractor, check references, ask how long they have been in business and how many systems they have installed like yours. Check if they insured and licensed with your regional building department.