Lato with Roboto Slab in action on everywhere.is

.header-1 { font-family: Lato, sans-serif; font-size: 42px; font-style: normal; font-weight: normal; letter-spacing: normal; line-height: 53.99974060058594px; text-transform: none; color: #323232; }
.content-1 { font-family: Lato, sans-serif; font-size: 30px; font-style: normal; font-weight: normal; letter-spacing: normal; line-height: 40.50008010864258px; text-transform: none; color: #323232; }
.content-2 { font-family: 'Roboto Slab', serif; font-size: 18px; font-style: normal; font-weight: normal; letter-spacing: normal; line-height: 27px; text-transform: none; color: #323232; }
.content-3 { font-family: 'Roboto Slab', serif; font-size: 18px; font-style: normal; font-weight: normal; letter-spacing: normal; line-height: 27px; text-transform: none; color: #323232; }
Lato is available from Font Squirrel, Google Web Fonts, Open Font Library and Typekit.

Roboto Slab is available from Font Squirrel, Google Web Fonts and Typekit.
Found by @mikesten on 13 Feb 2014.

Lato with Roboto Slab