Skipmore.com is a great collection of retro/old school/8bit pixel based games. All games are short, sweet and loads of fun. Perfect! The site is in Japanese but there is no language barrier and most games use English in-game. Start from the homepage (skipmore button) to choose games. The rest of the navigation is mostly galleries of screenshots, development blog, etc.
Some game highlights are:
A short and lovely adventure quest.
Synopsis Quest Deluxe
A collection of RPG-themed mini-game gags that make you feel like you've embarked on a full-fledged adventure. You can start from the beginning and play in order, or jump around and even play the last scene first. Clear all of the quests to get the winning screen. Vintage style Famicom music sets the mood.
A highly addictive hunt that is harder than it first appears to be.
Bookmark and have fun!