I bought two filter wrenches for use at work off of the truck.
Channel lock adjustable wrench.
http://www.channellock.com/acb...ID=26
Lisle spring loaded 3/8 drive wrench.
http://www.lislecorp.com/tool_...=1051
I used to use the channel lock one on my car untill I got the lisle one. The channel lock one is nice but sometimes you just cant get a good grip or any decent roration due to the filter location. I solely use the lisle one now and its a breeze.
I also use a medium size pipe wrench at work, or the shadetree punch and hammer, for the large (6"-7" round

) hydro filters I can barely grip
