In Yume Nikki (Dream Diary), you're cast as a young girl living in a small apartment. There is very little to do in your room, but fall asleep and an entire dream world is yours to explore. Go to sleep, dream freaky-ass dreams, collect 'effects', see uboa. While the main 'aim' of the game is to collect all the various effects, the real meat of the experience comes from the huge maps to explore. Many of the wide-open areas loop around on themselves so searching everywhere can often feel a little daunting, but keep an eye on the odd landmark here and there and you should be alright.
Press Z to intereact with the creatures or to pick up effects. Press x to open your menu and activate an effect. Press 1 to 'use' certain effects. If you get very lost (or attacked by a Toriningen) press the 9 key to wake up.
Since its release (in its current state) in 2004, Yume Nikki has built up a significant cult following from all corners of the Internet. Download it here.
Uboa is a fansite of sorts, running on a 4chan-style imageboard. It's similar to a regular internet forum, with higher emphasis on images and no registration. Anyone can post and while everyone has the option to remain anonymous, they can always post with a name and/or email address to make themselves more immediately recognisable.
There are separate boards for discussion of each of the main characters (though a little overlap will be forgiven) along with a creatures board, a general discussion board and a dreams board. There are also several low-traffic off-topic boards and an art board with an in-built java paint application. Last of all, we have an IRC channel on the Rizon network, accessible from the menu on the left.