So, I have gentoo up and running on my T40, and thought I'd share the resources that helped me get there.

For those interested, here's the currently running kernel config.

Preparation:
I wiped the predesktop area. I don't plan on running windows, and I'd rather have the disk space, thanks.

2.6 Kernel / Modules:

• Power Management - I stuck with APM rather than ACPI. I may try ACPI later, but not yet.
• Graphics Support - I went with framebuffer support this time, and so far, I like it.
  Make sure you compile framebuffer console support INTO the kernel.
• Sound Support - Alsa + snd_i8×0, as usual
• Networking
  • e1000 driver worked out of the box for the on-board Ethernet card
  • There is a new SF project providing a driver for the onboard Intel Corp. PRO/Wireless LAN 2100 card. The driver seems to work fine, I've not been using it long enough to complain.. Also, there is a nice ebuild for centralizing wireless config. Sweet!
    • emerge wireless-tools
    • emerge wireless-config
    • tweak /etc/conf.d/net and /etc/conf.d/wireless as recommended by wireless-config package
      Noteable: associate_test_eth1="MAC" was required to allow dhcp to finish initializing. I also provided wireless dhcp settings in /etc/conf.d/wireless rather than in /etc/conf.d/net.
    • /etc/init.d/net.eth1 start

iwconfig  (before setting any wireless stuff up)
lo        no wireless extensions.

eth0      no wireless extensions.

eth1      IEEE 802.11b  ESSID:""  Nickname:"ipw2100"
          Mode:Managed  Channel:1  Access Point: 00:00:00:00:00:00  
          Bit Rate=0kb/s   Tx-Power=32 dBm   
          Retry  n   RTS thr=2304 B   Fragment thr  ff
          Encryption key  ff
          Power Management  ff
          Link Quality:0/100  Signal level:-66 dBm  Noise level:-98 dBm
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

lspci

0000:00:00.0 Host bridge: Intel Corp. 82855PM Processor to I/O Controller (rev 03)
0000:00:01.0 PCI bridge: Intel Corp. 82855PM Processor to AGP Controller (rev 03)
0000:00:1d.0 USB Controller: Intel Corp. 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #1 (rev 01)
0000:00:1d.1 USB Controller: Intel Corp. 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #2 (rev 01)
0000:00:1d.2 USB Controller: Intel Corp. 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #3 (rev 01)
0000:00:1d.7 USB Controller: Intel Corp. 82801DB/DBM (ICH4/ICH4-M) USB 2.0 EHCI Controller (rev 01)
0000:00:1e.0 PCI bridge: Intel Corp. 82801 PCI Bridge (rev 81)
0000:00:1f.0 ISA bridge: Intel Corp. 82801DBM LPC Interface Controller (rev 01)
0000:00:1f.1 IDE interface: Intel Corp. 82801DBM (ICH4) Ultra ATA Storage Controller (rev 01)
0000:00:1f.3 SMBus: Intel Corp. 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) SMBus Controller (rev 01)
0000:00:1f.5 Multimedia audio controller: Intel Corp. 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) AC'97 Audio Controller (rev 01)
0000:00:1f.6 Modem: Intel Corp. 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) AC'97 Modem Controller (rev 01)
0000:01:00.0 VGA compatible controller: ATI Technologies Inc Radeon R250 Lf [Radeon Mobility 9000 M9] (rev 02)
0000:02:00.0 CardBus bridge: Texas Instruments PCI1520 PC card Cardbus Controller (rev 01)
0000:02:00.1 CardBus bridge: Texas Instruments PCI1520 PC card Cardbus Controller (rev 01)
0000:02:01.0 Ethernet controller: Intel Corp. 82540EP Gigabit Ethernet Controller (Mobile) (rev 03)
0000:02:02.0 Network controller: Intel Corp. PRO/Wireless LAN 2100 3B Mini PCI Adapter (rev 04)

References:

• Linux on the IBM Thinkpad T40
• Gentoo linux on a Thinkpad T40p
• Linux on the Thinkpad T40
• Linux on the Thinkpad T40p - includes ACPI and Multihead X

• Thinkpad Configuration Tools for Linux
• thinkpad-linux archives
• linux-on-laptops: IBM
• Intel® PRO/Wireless 2100 Driver for Linux
• wireless-config ebuild
• Linux on IBM T41p

Other Notes:

• Gentoo: The X Server Configuration HOWTO
• Gentoo: Gentoo Linux ALSA Guide
• console framebuffer [Solved]
• radeon DRI howto
• Gentoo: Howto APM Suspend
• X.org: xorg.conf (5) manpage
• Gentoo Forums: Linux Memory Management or 'Why is there no free RAM?' - also, why you may not see some of your RAM (i.e. amounts over ~800M)
• And She Was: T23 and Dual Monitors

X Font Server and X11:

Finally, an email that concisely explains what the hell 'unix:/7100' actually DOES...

X Font Problem

From: Nadav Har'El

On Mon, Jul 09, 2001, Alexander V. Karelin wrote about "Re: X font problem":
> 1. The unix/:-1 thing is very simple. unix stands for transport. / has to
> preceed the hostname. If the host is local, than the column follows the
> slash. And the last part is the number of the port, which for unix
> sockets, is -1. So - if You want to use Your font-server's resources -
> first check which transport/port does it serve on. And than add it to the
> fontpath.

...

Anyway, what I'm trying to say is that -1 isn't exactly a port number, but
rather a hint the X server and/or font server use to find this file.
For example, in my Redhat 7.1 installation, I have in XF86CONFIG
FontPath "unix/:7100"

This 7100 is not a port number, since unix-domain sockets do not have
port numbers (an example where this would have been a port is with the
tcp transport: tcp/somecomputer.com:7100 - see man X(7) for more info).
This 7100 tells X to use the local file:
# ls -l /tmp/.font-unix/fs7100
srwxrwxrwx 1 xfs xfs 0 Jul 9 23:15 /tmp/.font-unix/fs7100

Which the font server (xfs) is listening on. Note the "s" in the beggining
of the ls -l line: this says this is a special unix-domain *s*ocket file.