Museo Slab is a serif font. It goes well with Museo Sans, Open Sans, Noto Sans, Old Standard, Proxima Nova, Lucida Grande, Entypo Social, Entypo Logo, Museo and Futura PT. If you're thinking about using Museo Slab then try 40px for headers. Give 16px a shot for content.
People commonly tag it as slab serif, blog, writing, elegant, design, classic, sans serif, photo, programming and tech. You can get it from Font Squirrel, Fontdeck, Fonts.com, Fontshop, Fontspring, MyFonts and Typekit.