When I first saw the Drawdio at Maker Faire I knew it would be a great project for beginners: A lot of fun with instant gratification! Essentially, it's a very simple musical synthesizer that uses the conductive properties of pencil graphite to create different sounds. The result is a fun toy that lets you draw musical instruments on any piece of paper.
This is actually not any sort of product or public project (!) - its something I designed to help me evaluate solar panels and how they act when charging batteries. Normally this requires a lot of multimeters and its a bit of a pain to do if you have to constantly change out panels. So I decided I would build a specialized tool that would assist me.
A good front-light is essential, not only for being seen, but to see the road. LED lamps will not illuminate the road, and they can be too dim for cars to see you (1W or better LEDs are quite nice as headlamps.) I offer here a simple (but high-quality) design to build your own 5 or 10W halogen lamp, which runs off of a rechargeable 7.2V or 7.4V Lithium Ion battery pack.
Arduino is a great starting point for electronics, and with a motor shield it can also be a nice tidy platform for robotics and mechatronics. Here is a design for a full-featured motor shield that will be able to power many simple to medium-complexity projects. Build the kit, and learn how to use it with these detailed instructions.
The Brain Machine provides you with a fun, easy way to meditate, all the while being very photogenic! They work with lights and sounds that pulse at a 14-minute-long meditation sequence of brainwave frequencies. Your brain synchronizes to this meditation sequence, and you meditate. It's that easy! And the beautiful colors and patterns you vividly imagine along the way make it fun and enjoyable.
In 1970, John Conway came up with a 1-player game called Game of Life. The Game of Life is a mathematical game that simulates 'colonies' that grow or die based on how crowded or lonely they are and is known for the way it creates a beautiful organic display out of randomness. Here is a design for a simple electronic project that plays Conway's Game of Life. Make one kit and keep it on your desk, or attach multiple kit modules together to create a large display.
This project combines a whole heap of modules to enable a Raspberry Pi to power a large 1.2 inch 4 digit 7 segment display. A small switch switches the display between showing the temperature and the current time. The project uses a real-time clock (RTC) to ensure that the Pi always has the correct time, even if it is not connected to the Internet.
Have a lackluster datasheet for your sensor, but a demo app from the vendor that seems to calculate the value you need? If the app is written in .Net (Visual Basic or C#) -- and if it's Windows based, it probably is -- you might be able to decompile the app and find that magic formula you're looking for!