Consumer Reports has some chilling results from crash tests done of child car seats.  The magazine says it can recommend only 2 of 12 seats tested. Those that passed the test are the Baby Trend Flex Lock and the Graco SnugRide with E-P-S.  In frontal crashes at 55 kph and side crashes at 60 kph,  most of the seats either came off at their base or twisted in place.

Source: AM800 @ 2007-01-05 07:24:45

Consumer Reports is known for taking safety to the next level, and in its
most recent round of testing rear-facing, infant car seats, it went beyond
the current federal safety standards for seat performance in a collision.
The government tests seats in front crashes of 30 mph, but Consumer Reports
simulated front impacts of 35 mph and side impacts of 38 mph (the same
standards used for car safety testing). The results in this more stringent
environment were dramatic, with 10 of the 12 seats either twisting too far
or coming out of their bases.

Consumer Reports' testing also showed serious failings in seats secured by
the LATCH system. The National Highway Traffic and Safety Administration (
NHTSA) itself calls the LATCH system confusing and Consumer Reports notes
that the NHTSA is planning a public hearing on the system later this year.

Here's how the seats fared in Consumer Reports' tests:

The Good
Baby Trend Flex-Loc Adjustable Back
Graco Snugride with EPS

The Bad
Chicco KeyFit
Peg Perego Primo Viaggio SIP
Compass I410
Evenflo Embrace
Britax Companion
Graco SafeSeat
Safety 1st Designer
Combi Centre ST
Evenflo Discovery
Eddie Bauer Comfort