The Starwood American Express:
up to 10k bonus points in the first year, including 4k with first use
earn Starwood hotel points (W/St Regis/Sheraton/Westin) which can be used for hotel stays or converted 1:1 into miles with most airline programs
convert 20,000 points and get 5,000 bonus points -- which mean you actually earn 1.25 miles per dollar on all purchases instead of 1 mile per dollar
free the first year, $30 thereafter
converts 1:2 into qantas and air new zealand!

You can also see my blog post on credit card miles.