1) Mob Spawners will spawn only 6 mobs if the mobs are in the 16x16x8 (length x width x height) cube area around the mob spawner. Take them out of the range and make them spawn over 6.

2) Villages merge when the closest doors from village A and village B are less than or equal to 64 blocks distance apart and will become one 1 village instead of 2.

3) This is how you can look into your personal logs. For instance, you caught somebody using cuss words in the Planet Minecraft server, or insulting conversations. If you need "Proof" for the moderators, then this is how to get your proof. Go to the .minecraft folder, click the log folder, and click on the log that was recorded on the day when it happened. There are multiple logs of the same date, so you might have to search a bit for just the right log.

4) You can get a secret block called the smooth double stone slab with the following command:
/give (username) 43 1 8

5) You can't lure animals in the end with wheat.

6) Stacked Snow Layers adjusted to the height of a snow block do not count as a Snow Block and will be washed away with water unlike the snow blocks.

7) Sugar Cane does NOT grow faster on sand.

8) These are 2 ways on how I obtain food underground.
-Make a fishing pole, drop down a water source block and fish in the full source block.
-Punch one zombie to death. It will spawn more zombies and you will gain many rotten flesh.

9) Silk Touch Shears do not lose durability when a glass is being broken.

10) Mobs try to avoid walking on rails.

11) Dragon Eggs are falling sand entities. Therefore you can obtain them through placing a torch under the supporting block holding the dragon egg, then breaking the supporting block.

12) Spawn Chunks are always loaded unlike other chunks which are unloaded when you are not near.

13) If an item is thrown into the nether portal and into the other dimension, then where the nether portal is constructed on the other side's chunk will be loaded for exactly 1 minute.

14) Press F3 + b to know the hitboxes of every single entity. (Special Thanks to Peter- and Squashman)

15) If you push boat into land they can destroy snow. (Special Thanks to Squashman)

16) Skeletons and Zombies do not burn in sunlight when they stand on soulsand.

17) TNT can destroy lava.

18) Mushroom blocks can be used as fuel. (Special Thanks to Squashman)

19) You can repair Chain Armors with iron ingots on an anvil. (Special Thanks to Sqaushman)

20) You don't need to completely craft a compass or a clock to see what time it is or what direction you need to go. Just put the recipes in the crafting table, and it will show you even if you haven't crafted it.