Canva is seriously awesome and i'm glad someone finally thought of this idea. If you're not a designer, Canva has a very easy UI to help you design anything from facebook covers to posters. There's great free content, and they only charge if you want to use specific images or templates. You can always upload your own images free of charge.
I found this site a great resource to organize my wedding and find all of my vendors. We ended up using a lot of great vendors we found through WeddingWire, as well as using the seating arrangement tool and building our wedding website.