Avenir in action on quiver.net

Under the hood

.header-1 { font-family: AvenirLTStd-Light, Helvetica, Arial, sans-serif; font-size: 32px; font-style: normal; font-weight: normal; letter-spacing: -1px; line-height: 42px; text-transform: none; color: #FFFFFF; }
.content-1 { font-family: AvenirLTStd-Book, Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; font-weight: normal; letter-spacing: normal; line-height: 24px; text-transform: none; color: #DEEBEB; }
.content-2 { font-family: AvenirLTStd-Book, Helvetica, Arial, sans-serif; font-size: 18px; font-style: normal; font-weight: normal; letter-spacing: normal; line-height: 24px; text-transform: none; color: #DEEBEB; }

Avenir is available from Fonts.com and MyFonts.