Avenir in action on mixlr.com

Under the hood

.header-1 { font-family: "Avenir LT W01 85 Heavy", "Helvetica Neue Heavy", Helvetica, arial, sans-serif; font-size: 32px; font-style: normal; font-weight: normal; letter-spacing: normal; line-height: 44px; text-transform: none; color: #333333; }
.content-1 { font-family: "Avenir LT W01 55 Roman", "Helvetica Neue Roman", Helvetica, arial, sans-serif; font-size: 18px; font-style: normal; font-weight: normal; letter-spacing: normal; line-height: 27px; text-transform: none; color: #333333; }

Avenir is available from Fonts.com and MyFonts.