Here's a list of things not to do in your Mario levels, consider it advice for when Super Mario Maker comes out in a week and a half. Also, here's things not to do in your Mario overworld. They both come from the rom hacking community at SMWCentral.
Stephen Totilo of Kotaku tries to determine the correct chronology for all the games in the Super Mario canon.
Here are fan-translated Game Center CX (previously) Episodes on YouTube: #1: Atlantis No Nazo, #2: Challenger, #3: Ghosts 'N Goblins, #4: Konami Wai Wai World, #5: Metroid, #6: Solomon's Key, #7 & #8: Prince of Persia: Part 1 - Part 2, #9: Mega Man II, #10: Super Mario 3. Much more after the break.... [more inside]
Super Mario Brothers X The greatest fan game tribute to Super Mario of all time! Gameplay video here. hat tip to tigsource!
Do Do Do Do Do Do Do Do Do Do the the the the the the the the the the Mario! Mario! Mario! Mario! Mario! Mario! Mario! Mario! Mario! Mario!
Enough Plumbers (Flash game), a nice twist on a classic game: "It's when the plumber encounters the coins, though, that everything changes. For every coin you collect you also get a cloned plumber who copies every move of the original. Just trying to jump ten hapless clones at once onto a small platform and you can see how things have changed." (review) (via waxy.org)
A game developer resigns in style [possibly autoplaying music]
Mario Adventure - SMB3 hacked into an entirely new high-quality game
SMW - The complete soundtrack to Super Mario World, covered by one man using dozens of instruments. Roughly in game order, faithful to the originals, with some bizarre artistic license thrown around. A private hobby made public. Dedicated to Koji Kondo.