We have computed the very first chosen-prefix collision for SHA-1. To put it in another way: all attacks that are practical on MD5 are now also practical on SHA-1.
We have reduced the cost of a collision attack from 2^64.7 to 2^61.2, and the cost of a chosen-prefix collision attack from 2^67.1 to 2^63.4.
Demo: The legacy branch of GnuPG (version 1.4) is vulnerable. We have created two PGP keys with different UserIDs and colliding certificates.