European microchip registration database: you can use it to check whether a chip is registered elsewhere than in Belgium.
Official Belgian registration database for dogs
Official Belgian registration database for cats
Registration database of microchips for all animals except dogs: here you can find cats registered before 2017.
If you are wondering if what your animal has eaten is poisonous
All about the cat, in English, but very reliable
All about rabbits
Government portal on pets
About fleas and ticks, and so much more about the health of your dog and cat
Aid organisation for wild animals in need across Belgium.