Tong Family

At least for nerds. We looked at building a quadracopter, but at $500 for the kit plus $400 for a RC controller (?!!), it does seem a little expensive. Still for $1500, you can get a drone which flies for 15 minutes, gives you a first person view through a small CCD camera and has a heads-up display as well as carrying a high resolution Go Pro for unbelievable photos and videos. Pretty neat.
So onto other projects. Right now a 3-D printer is pretty cool particularly the Reprap movement where you use the printer itself to print its own parts (?!!). Pretty cool and a good introduction to mechanical engineering, but there are a dizzying number of different models to choose from with kit prices varying from $200 to $3K!.
Some good recommendations from robotgarden.org where they recommend:
DIY 3D Printer ← Robot Garden

Prusa Mendel – A good beginner machine with a large build size and a great way to not only learn about the hardware but the firmware/software as well. This is also where I started.
Ecksbot This is a very good variant of the Prusa design. I have used some of the parts of this design when I was modding my first machine while I tested things out for iron out what I needed.
Huxley Similar to the Prusa this little opensource printer has a build size of 140x140x110mm and is smapper and more portable than the Prusa.
Ronthomp Mendel: This Prusa variant follows more of the path of a fully self replicating printer by making more of its structure out of printed parts.
Mendel MAX: Unlike the Ronthomp Mendel the Mendel Max (looks to be inspired by the Prusa V2) and the Mendel Max 2.0 (looks to be inpired by the Prusa V3) goes the opposite direction with making its structure out of sturdy extruded aluminum tubing. This gives it a very rigid platform. Overkill?? Some say not. You decide.

 
What you need to know about buying a 3D printer | Cubehero

Some people are drawn to 3D printing because they like hardware or mechanical machines and would like to build their own from scratch, from kits, or design one of their own. For them, the fun of it all is the actually building of the machine.

What you need to know about buying a 3D printer | Cubehero

The RepRap family of 3D printers are the poster child for DIY 3D printing. Specifically, the MendelMax 1.5 comes to mind, as a DIY 3D printer that’s pretty solid as well as easy to assemble.

What you need to know about buying a 3D printer | Cubehero

To see what other people have imagined, you can visit our site, Cubehero.com to see what people are hosting. Other notable places to check out are GrabCAD.com and Thingiverse.com

What you need to know about buying a 3D printer | Cubehero

The cost you’re willing to pay for a 3D printer will figure heavily into what kind of printer you will buy. As a rule of thumb, kit-based printers are cheaper than pre-assembled printers, and self-sourced printers are cheaper than kit-based printers. However, there are solid pre-assembled printers available for $500 to $800.

What you need to know about buying a 3D printer | Cubehero

The Solidoodle and the Printrbot Jr are two prime examples of value 3D printers with reportedly consistently good prints for a low price.

What you need to know about buying a 3D printer | Cubehero

Delta printers are based on pick and place robot designs that tend to have really fast performance. The Rostock Max (kit: $999) clocks in at 300 mm/s, and as evident by pick and place machines, they can only get faster. The first delta printer to arrive on the scene with a significant following is the Original Rostock by Johann Rocholl. His next iteration is the Kossel. [You can make the Kossell with OpenBeam and print its parts too. pretty cool]

 
OpenBeam Kossel Pro – A new type of 3D Printer by Terence Tam — Kickstarter

A fork of the ground breaking Kossel 3D Printer, with all 3D Printed parts injection molded for ease of assembly and cost reduction. [This seems like an incredible unit. It is delta robot based system and uses Openbeam parts]. $1K gets you the first kits due in December 2013! and it is based on the Kossel