Here are links to some outstanding projects, and some of my personal picks, on LEGO CUUSOO. I will try to list mainly good ones that don't have much support. Go and check them out, and perhaps support them.
Ultimate Collector's Series Lightsaber
Description: A series of life-size, extremely detailed collectable lightsabers. The creator also plans to add a stable blade!
Description: I have a kind of obsession with things like this, and a motorized LEGO rollercoaster would be awesome to own. Another LEGO rollercoaster project, featuring a whole system of rollercoaster bricks, is here (This one is created by RCcreator1).
Pinball Machine with 7 flippers 3 floors 2 rails 1 ramp multiball nachapon bbqqq
Description: A real, working LEGO pinball set! Watch it in action here.
Description: A cool space theme (nothing to do with Warhammer). The thing that makes this projects stand out is the amazing concept art produced using Blender. Go and have a look (this one has quite a bit of support, but it's my favourite).
Description: An interesting and unique theme involving bad guys that are attempting to destroy the environment with a variety of machines, and a team of heroes defending the environment with more (eco-friendly) machines. This project also has some great concept art. This one is very new, so it could do with some support!
Description: Muppets. In LEGO. Don't they just belong together? This one has lots of great sketches of potential minifigures and sets.
Description: This one features several excellent LDD models of dragons, but has gone largely unnoticed. Support it!
Star Wars Modular Buildings/Locations
Description: Many of you may know of ACPin, and his gigantic and spectacular Star Wars MOCs (If you haven't, look here). If you'd like to own one, lend your support!
Description: I think LEGO Scrabble would be quite cool. Have a look at the project to get an idea of what it would look like.
Brick Rogers: The Galactic Girl from the 5th Cenury AE.
Description: A steampunk-ish theme, that could do with some support.
MINDSTORMS programming on Tablets & Smartphones
Description: Self-explanatory. But wouldn't it be useful?
More coming soon, as well as images. Please give suggestions.