Mat suggested a RC snubber, so it's a resistor in Serie with a capacitor, so will flow only for a short period of time.
You may find some explanation in the following document
http://focus.ti.com/lit/an/slup100/slup100.pdf
I would prefer to switch on the AC zero crossing to extend the relay contact lifetime...
OR you may decide to use some SSR... a bunch more expensive...
EDIT: ah crap, i'm late 
Also, probably a nice idea to place some 0.1 uF in parrallel with each realy coil + 100-470uF & 0.1uF on their VDD line.
Last edited by mister_e; - 3rd February 2007 at 15:14.
Steve
It's not a bug, it's a random feature.
There's no problem, only learning opportunities.
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