Well, I am getting two older laptops ready for the e-waste recycle and I needed to delete all the data on the hard drives. There are several utilities out there to do this but I think the easiest and feature rich option is DBAN. You can build a bootable CD and it will allow you to delete all the data on the drive to several different specification like DoD 5220-22.M Standard Wipe or RCMP TSSIT OPS-II Standard Wipe.
I highly recommend wiping out the drives prior to dropping of equipment at most e-waste facilities. Often companies that operate as e-waste collectors are reuse/recycle facilities so if your machine is in working order they will take it and either donate or sell it. There is no guarantee that they will wipe the drives out prior to selling or donating the hardware which means someone could easily boot your system up and have fun trying to recover your data. In this day and age there is no reason to take that sort of risk.