there is many information available about running Linux on the T42p here, but I want to share some information I didn't find right away... first here is my kernel config.
All the hardware is very well supported just install the distribution of your choice and add things like:
the fglrx driver for the FireGL T2
if you run >= 2.6.10 you need to apply this patch to build_mod/agpgart_be.c in order to get it compiled
if you want to switch between X and console you need to comment out the Load glx in your X config file
the Madwifi driver for the Atheros wireless chipset
the Synaptics (touchpad) driver for XFree/XOrg
This will give you nice features like: switching off the touchpad clicking/tapping or what I like most a scrollwheel. The scrollwheel is simulated by disabling the normal mouse movements for about 1cm (0.4") on the right side of the touchpad (full configurable!). Up/Down movements in this region are interpreted as scrollwheel movements.
This is a must have!
get the latest version of the IBM ACPI driver
this will get you some nice features, also make sure to load the module with experimental=1 to get all features
powernowd for frequency scaling
also make sure to set the scaling steps to 200MHz instead of 100 which is the default, because the scaling can only be done in 200MHz steps and (for me) it seems to behave better when set to 200. I also changed the lower threshold to 30% instead of 20.
and last but not least install tpb to get all of your thinkpad buttons to work and a nice OSD (on screen display) for brightness, volume, etc...
I always bind the Thinkpad button (Access IBM) to spawn a xTerm :)
things to bee done are: ACPI suspend and maybe Laptop-mode