Microsoft's 800-BING-411, 800-CALL-411, and 800-555-TELL (Tellme) services are all announcing that they are discontinuing service effective June 1, 2012.
Google's 800-GOOG-411 was discontinued November 11, 2010.
Alternate free USA directory assistance services:
These other services do not offer to transfer a call like BING does. FREE-411 can also search residential listings, which BING did not do.
Google ended their reverse phone lookup web service around February 2011.
Google ended Gizmo5 on April 3, 2011.
I hope that Google Voice is not in jeopardy.