Congress: Search this site by ZIP code or state. Then click a member’s name and find all his/her contact information. You might want to double check with http://congress.gov, which is a reputable information resource, but difficult to search in this way.
Locally: Your state’s official website with information about your state legislature is easy to find. Either type in www., your two letter state code, and then .gov. Or, type the full state name followed by .gov. So, www.il.gov or Illinois.gov takes you to the official website for Illinois. Most states have both forms.
Influencers: Open Secrets is a reputable data aggregation site regarding those who contribute to political campaigns. Click on Industry to see who the players are in your sphere.