Canva – A simple tool to make really nice graphics for your blog and social media.
Piktochart – Pretty much the same as Canva. A tool to create nice infographics and presentations. Note that all your designs will have piktochart logo at the bottom unless you pay for a premium version.
Befunky – Not so popular as Canva or Piktochart but there is photo editor, collage maker and the designer with pre-built templates for social media etc.