Here are some DIY projects that I'm or I've been working on my in spare time

Naza related

• DJI NAZA GPS communication protocol decoder (aka NazaDecoder)
• DJI NAZA/Phantom CAN bus communication protocol (aka NazaCanDecoder)
• DJI A2 CAN bus decoder library (beta) (aka A2CanDecoder)
• Naza GPS module alternative (using APM 2.6 GPS/compass combo)

OSD related

• Library for FrSky PixelOSD
• RemzibiOSD support for MultiWii v2.2
• DJI Naza-M adapter for RemzibiOSD (based on NazaDecoder and NazaCanDecoder)
• DJI Naza-M adapter for MinimOSD (based on NazaDecoder and NazaCanDecoder)
• Easy to use Voltage Divider library for Teensy 3.x
• iOSD Naza-M v2/A2/Wookong-M log to GoogleEarth KML converter

FrSky related

• Easy to use and highly configurable FrSky S-Port telemetry library for Teensy 3.x and 328P based boards
• Easy to use and highly configurable FrSky old telemetry library for Teensy 3.x and 328P based boards
• Fixing broken FrSky FLVSS OLED display
• FrSky STK alternative using Arduino Nano 328P/168

Gimbal related

• Bluetooth connector for DYS 3-axis gimbal

AR.Drone related (mainly on ARDrone-Flyers forum)

• DIY flight recorder using SiRF IV GPS (for less than $50)
• DIY flight recorder using any (NMEA) GPS
• Big motor adapter for AR.Drone (done together with Schlauncha) - to better familiarize yourself with the project you may start reading from THIS POST
• AR.Drone flying over 3G network
• http://mirumod.net - I'm not the autor of the MiruMod itself, but I've created the webpage (now maintained by miru).

Here is the proof