LOGO LAB will assess your logo on 10 key factors like balance, scalability, color blindness, recognizability etc. All you have to do is upload your logo in PNG or SVG format.
LogoLounge.com is one of my favorite sites. Talk to me about student access.
A lot of designer develop quick Mood Boards to help them work through related visuals and determine the direction they want to take with their design. Check out this free, easy-to-use mood board HERE: Moodboard