Western Digital, Seagate, Lacie are amongst the top. Interface is a matter of preference and availability. If you have a modern machine with SATA disks, you may want to find out if you have the ability to use ESATA external disks - faster than anything else as they plug directly into the SATA control system
Other than that, FIrewire 800 or USB2 is the way to go. 3.5inch for desktops, plus a 2.5inch portable with a good sized disk. 3.5" disks are cheap, even the ESATA versions when compared to the 2.5", but do go for as big a disk as you can afford to get - you will use it! One of the beauties of External disks is that you can backup and then leave the disk with someone else - off-site backup is great for peace of mind.