The lt_hotswap kernel module enables hot-swapping for disk drives with full DMA support under Linux. It should work on any laptop with hot-swappable bays and ACPI support.
Latest version: http://churchofjim.org/sources/lt_hotswap-0.2.0.tar.gz
Development and discursion of lt_hotswap is currently being held in Linux-ThinkPad Mailinglist. Current highlights of discussion and user experiences follow:
In order to use the driver you must also have the ibm-acpi driver linked to your kernel (module or compiled). When loading the hotswap module, you can use module parameter
to automatically unregister IDE drive interfaces and eject the drive automatically by the kernel. This will happen upon popping out the ultrabay lever.
Users report success with T22 and T40 on mailing list, although many other models should also work.