I just found the following after a quick google search. Hope they help. Its not clear if you want to use IR like a household remote control (relatively easy) or use the IR technology in new laptops and handhelds. The IrDA link should help for the 2nd case, for remote control, try the third one.
* The IrDA organization is the originator of SIR (Serial IR, 115 kbps), FIR (Fast IR, 4 Mbps), and other specifications. http://www.irda.org
* A primer on Standard Consumer IR, used in remote controls and other consumer devices. From Standard Microsystems Corp. http://www.smsc.com/main/appnotes.html
* IrCOMM2k is a free, open-source Virtual Infrared COM Port for Windows 2000/XP
* Ziplabel has schematics and code for a free, basic computerized infrared remote project.