I’ve been a DragonFly BSD committer since mid 2009, and have since contributed to several parts of the OS, mostly to the kernel and drivers as can be seen in the non-exhaustive list below.

Contribution Description Release
DevFS Device File System 2.3
Active Disk Probing probes for on-disk metadata on connection of device 2.3
unix98 PTY support   2.3
Writing/updating/porting several drivers (e.g. hifn, glxsb, cs5536, nsclcsio,kbdmux, vn, aesni, ubsec, …)  
Kernel minidump support ported from FreeBSD 2.5
GPIO framework a lightweight GPIO framework, modelled after OpenBSD’s 2.5
Watchdog framework a lightweight watchdog framework 2.5
Linux Emulation updated to Linux Kernel 2.6 syscalls 2.5
dsched an I/O Scheduler Framework, allowing for pluggable I/O scheduling policies 2.7
dsched FQ policy a dsched fair queueing policy 2.7
proplib ported from NetBSD 2.7
dm device mapper, initially ported from NetBSD, mostly rewritten by now 2.7
dm_target_crypt A disk encryption target (think dm-crypt) compatible with Linux’ cryptsetup, but written from sractch 2.7
initrd support Support for an initial ramdisk, a la Linux initramfs, which can be used to mount a supported FS from any volume as root mount (e.g. LVM, crypt, ISCSI volumes) 2.7
udev, libdevattr A device enumeration library and supporting daemon 2.7
opencrypto SMP improvements involved in improving the performance of the software crypto (cryptosoft) by taking advantage of multiple CPU cores, as well as several fixes 2.7
opencrypto AES additional ciphers Implemented AES XTS, Serpent CBC and XTS, Twofish CBC and XTS in opencrypto 2.7, 2.11
utmpx and wtmpx support   2.9
VIA Padlock RNG driver Added support to the VIA padlock driver to feed the kernel with entropy 2.11
libdm libdm is a simple BSD-licensed device mapper library that is API-compatible with libdevicemapper 2.11
tcplay and libtcplay tcplay is a simple BSD-licensed tool that allows reation, managing and mapping of TrueCrypt volumes. It is written from scratch and 100% compatible with TrueCrypt 2.11
dfregress A small and UNIXy regression test framework and test driver 2.13