Updated to 2.6.32.61 LTS
Includes bugfixes and optimizations over Nokia's 2.6.32.54 kernel
Includes Opptimizer
Overclocking!
Supports GPT GUID partitions
128 partitions on a 16GB N9? Why not!
Includes ExFAT
Supported: Read/Write
Enables NTFS
Supported: Read/Write
Enables NFS server
NFS Protocol Versions: 3 & 4
Enables btrfs
Transparent compression and snapshots and -ENOSPC! Yay!
Includes 802.11 injection
Surprise your neighbors who still use WEP!
Patched Aegis security (a.k.a. Open Mode)
Wouldn't be too useful without it, right?
Enables NAT routing

Code:

# tar xvzf linux_2.6.32.61-plus-20131128.tar.gz -C /
# depmod -a 2.6.32.61-plus

Use this kernel with ubiboot
Gone are the days of flashing kernels!

Be sure to depmod the new kernel, and add the kernel filename to ubiboot.conf

Instructions for installation without Ubiboot can be found here.
NON-UBIBOOT USERS: PLEASE READ THE FOLLOWING
There are apparently very valid reasons to not use it.
However, please do not spam the thread with help requests - you have chosen an unsupported installation method, a provisionary but complete one has been made.

Enabled btrfs support
Warning: Experimental disk format. Beware of dragons!
Enabled Netfilter REDIRECT target support
Misc:
btrfs bugfixes and subvolume boot support
driver core: Constify struct sysfs_ops in struct kobj_type (patch)

Introduce /sys/fs/cgroup
Enables systemd to run on Harmattan. Service scripts will need to be ported.
Enabled /proc/atags export
Misc: various minor tweaks

This is a major release.
Introduced and enabled Tiny RCU
Similar performance to HRCU, with lower memory footprint
Unified EXT2/3/4 fs driver
Introduced and enabled Interactive CPU governor
Jumps straight to the maximum enabled OPP, on the basis of 'race-to-idle'
ARM: generic early_parameter() support
Moves the ARM-specific __early_parameter() to early_parameter(). No functional change.
Additional packet injection fixes (nieldk)
Misc: various minor bugfixes.

Enabled CONFIG_WL12XX_SDIO_TEST=m (nieldk)
Fixed building Opptimizer kernel modules after a 'make mrproper'

Enabled support for NFS server, versions 3 and 4
Enabled NTFS filesystem driver
Introduced ExFAT-nofuse filesystem driver (sourenaraya)
SPECIAL NOTE: While the ExFAT kernel driver is open source, it is still patent-encumbered. Please ensure you have a license to utilize it in countries that observe software patents.
Introduced Opptimizer kernel modules, integrated with the kernel build tree

Updated to kernel.org 2.6.32.61 incremental patch (.60, .61)
Fixed task selection priority bug (juiceme)
Enabled NAT routing (jackburton)

Initial release
Updated to kernel.org 2.6.32.59 incremental patch (.55, .56, .57, .58, .59)
Aegis neutered Open Mode patch
L2EN on kexec patch (juiceme)
2.6.32-ck2 patchset
ramzswap kernel notifications
Enabled GPT GUID support

r6: kernel-plus-61.patch.gz
note: the format for patches has changed - apply onto mainline 2.6.32.61 from kernel.org.

previously: kernel-plus-harmattan@github
the git repo will be updated when I have time - I can't seem to match some commits!

Code:

$ patch -p1 < kernel-plus-61.patch
$ make rm581_defconfig
$ make