If your question is actual use this web-site http://ru.vfsglobal.co.uk/allaboutyourvisas.html This is oficial web-site of Russian visa center. Click on visa type at the left hand side and find documents required. You can get invitation from a hotel (if you book a room there). Just write a e-mail and ask about it. My friend used this site and paid only visa fee (no any agent fees).

I invite you to visit Ukraine! Carpathian mountains and Crimea - fabulous places for recreation.

This site tells you everything. I used them - cheap and quick ! http://www.waytorussia.net/Travel/VisaSupport.html