Play through all four missions of Ruckingenur II (the hardware reverse engineering game!) Then all the missions of the Community Edition, Ruckingenur CE. Also, create your own missions with the level-editor

Build your own workbench/desk

Build your own bench power supply

Build your own Arduino (Breaduino/Hackduino)

Contribute to an OpenSource project that matters to you.

Program your TI MSP430-based MCU in linuuuuxxxxxx

Build your own Graphing Calculator

Build your own Simplex and Phantom circuits for multiple comm channels

Be able to explain and demonstrate PWM

Get your Ham Radio License (Technical class)

Improve on this walkie-textie

Participate in a Jump Team Competition

Concept from hand-drawn notes to CAD (OpenSCAD, Eagle, Altium, KiCAD, PADS layout), to implementaion.

Practice good bare-metal/systems programming habits

Parallel programming with Occam and Arduino

Parallel Programming with Propellor

Build projects for OpenMPI (C/C++)

Learn Erlang

For a week, use one of the the following: http://www.khanacademy.org/, mathWays, integrals.wolfram.com

Write scripts to interface with Google services

Website User testing

Design websites that can be viewed on various screen sizes (desktop/cell phones/smartphones/tablets/etc)

Try text-only editors such as nano, (tiny)vi/m, and emacs.

Try other html/css editors such as SublimeText with ZenCoding plugin, jEdit, Notepad++, gVim

Try unix tools on Windows with Unix tools for Windows, SysInternals, MSYS, and cygwin.

Build an Android app in AppInventor

Build an Android app in SL4A (Lua, python, perl, etc)

Setup Android SDK in Eclipse and re-build your android apps.

Build a game in Scratch

Build a game in GameMaker

Build a game in jMonkey

Action Adventure Video Game Level Design: Basic Level Diagrams

Action Adventure Video Game Level Design: Detailed Level Plans

Action Adventure Video Game Level Design: Pacing, Content. Mood

Script your games with your own scripting language using Xtext (Eclipse 3.6 Helios) or yacc/bison and lex.

Build a game using DirectX

Build a game using OpenGl

Build a game using the some other game engine like torque.

Push your game to Steam, YoYoGames, or other distribution system.

Defend against PPTP and IPv6 VPN flaw

Exploit then fix bugs in Guyere

Exploit then fix bugs in Damn Vulnerable Linux

Exploit then fix bugs in the Metaploitable VM

Learn to use metasploit and armitage

Learn to use crypt(1)

Create your own self-signed certificate for use in a web server.

Create your own cipher

Use Nagios, nmap, The dude, and wireshark

Teach your skills to others in a public setting

For a week, try out a new linux (or other UNIX variant) distro such as Musix, live.linuX-gamers.net, CAELinux, CAINE (Computer Aided INvestigative Environment), Tinfoil Hat Linux, FreeBSD, or NetBSD.

Use Crooke's Radiometer to drive some engine/motor.

Replace (desolder/solder) puffy capacitors on your motherboard

CodeKata.pragprog.com

ProjectEuler

For a week, use one of the following: khanacademy.org, mathways, or Wolfram Alpha.