Watch out! DreamHost earlier tonight completely revamped their hosting plans and prepaid discount (for the better, I think).
http://Check out the new plan description here
I think the discounts are only visible on the signup page: https://dreamhost.com/signup/
The discounts are:
1 year: 9%
2 year: 18%
3 year: 27%
5 year: 36%
10 year: 45%
Note that the discounts now apply for the ala carte fees for a unique IP, premium phone support, double disk quota, double monthly bandwidth, VPN access, and SSL Secure Certificate. However, it's also worth noting that these options if selected at signup are now prepaid for the duration of your prepaid hosting plan. I'd guess that you can sign up for these features later on a monthly basis without the prepaid discount, but I'm not sure about that.
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