TuxOnIce
TuxOnIce (formerly known as Suspend2) is an implementation of the "suspend-to-disk" (or hibernate) feature which is available as patches for the 2.6 Linux kernel. During the 2.5 kernel era, Pavel Machek forked the original out-of-tree version of swsusp (then at approximately beta 10) and got it merged into the vanilla kernel, while development continued in the swsusp/Suspend2/TuxOnIce line. TuxOnIce includes support for SMP, highmem and preemption. Its major advantages over swsusp are: TuxOnIce was originally called 'Suspend2' because after the beta releases (at the time when Pavel forked the code base), there was  a 1.0 release and then a 2.0 release. The name 'Suspend2' developed as a contraction of 'Software Suspend 2.x'. Some efforts have been made over time to merge TuxOnIce into the vanilla kernel, but these have been opposed by Pavel, primarily (it seems) because Pavel believes much of the suspend-to-disk process can and should be run from userspace (see uswsusp), while Nigel Cunningham thinks this code belongs in the kernel. Nigel has stated both his desire and frustration in getting the TuxOnIce specific features merged back into mainline and is currently not actively pursuing for it.