Proxima Nova is similar and awesome.

Avenir
http://webfonts.fonts.com/en-US/Project/ChooseFonts#keyword%3Davenir

Apres RE at Webtype: http://www.webtype.com/font/apresre-family/

Judging by Twitter, you might just be able to use Gotham very soon.

from today's Ampersand Conference in Brighton UK also on twitter:

#ampconf Wild applause greets @H_FJ announcement that ‘100 per cent [about] of our fonts are available as webfonts’ #ampconf

p.s. Jonathan and I have the same eye glasses. Prada!

Any word on when they are making that release?

"soon" via http://www.typography.com/ask/faq.php?faqID=126#Faq_126

Jonathan said he was aiming for the next week or two, unless I'm mistaken. Here's a preview.

Strange slide there. I'm pretty sure I saw a substantially different presentation and interpret a longer schedule than everyone here so far testified. But what do I know, I'm only into the lenses.