Here are some non-random links:

Personal links:

rabenauge my demo group.
hunter a CBM8xxx open source tool by me. It helps to explore the CRTC.
Para’n’Droid open source of an old Android demo. Some parts were created by me.

Commodore PET:

Zimmers File Archives very cool Commodore 8-bit file area.
André’s 8-bit pages much info and documentation about the Commodore PET
CBMHARDWARE.DE German infos about the Commodore PET and others.

C128/C64:

6502.org Commodore documentation and more.
Retro Programming nice German blog about C64 programming.
VICE Emulator for many Commodore platforms.
z64k the currently best C128 emulator. But also for other platforms.

Vectrex:

VIDE very cool Vectrex stuff e.g. Vectrex-IDE,emulator and much more.
VecFever hardware to connect a Vectrex to a PC via USB.
PiTrex hardware for the Vectrex
www.vectrex.co.uk Vectrex stuff
PLAYVECTREX.COM other Vectrex stuff
WWW.VECTREX.DE German Vectrex stuff

Demoscene:

demoscene.info Infos about demoscene
Computerkunst e.V. based in Berlin
Digitale Kultur e.V. based in Cologne

Meadow / Forests

EinMannimWald German YouTube channel about forests
Der Selbstversorgerkanal German YouTube Selbstversorgerkanal

Various:

hinüber backpacks the best backpacks ever ;)
insaneOS is a lightweight operating system designed for Raspberry Pi Zero, Pi Zero 2, Pi1, Pi2, and Pi3.