Using the ENC28J60 Ethernet controller chip from Microchip, you can design a circuit to turn on your computer remotely. The entire documentation which includes photos, schematics, circuit diagrams and PCB layout is available at http://rototron.info/default.aspx?Page=WOL/WOL.aspx

This Internet-connected alarm clock provides three primary features: automatic time setting on power-up, streaming MP3 music, and remote management. The easy-to-use, PIC24FJ64-based clock is connected to an ENC28J60 Ethernet chip, an MP3 decoder chip for streaming music, an organic LED graphical display, and a 24LC512 EEPROM for storing alarm data, fonts, and images.