You have probably already build several LED light effects. These are simple to build as only microcontroller, resistor and LED is needed. But probably you will agree that flashing powerful lamps is more exciting and so dangerous as well. Rajkumar Sharma posted his 8 channel running lights controller that can handle 100W light bulbs on each channel.
Controller is based on PIC16F628 microcontroller which drives 8 opto-isolated triacs where each can handle 230V and 100W. Running lights effects can be changed with three tactile switches. If you planning on organizing party this might be a great next project.