If you're anything like me, the time you've got for photography is limited once you've factored in working/sleeping/eating/a social life (delete where appropriate). Therefore, any time you can save is automatically a plus, so FTP (File Transfer Protocol) upload is a very handy tool to have. This lets you batch upload your photos (time-saver), as well as ensuring that you don't have to endure the bleak, soul-destroying task of uploading your images one at a time (life-saver). Trust me, I've spent far too many hours uploading this way - make the switch as soon as you can!
I use FileZilla (a fairly popular choice, I believe - also a free one) and would thoroughly recommend downloading it from http://filezilla-project.org/ as soon as possible. If you're planning on uploading to iStockPhoto (I'll go through where I recommend uploading in my next blog), however, I recommend you instead use DeepMeta, which you can download off their website, since it let's you choose your categories in bulk before you upload your batch, so you don't have to go through and do it once everything's uploaded,
If you're really short of time, but still want to get your images in the review queue, FTP will upload your files in the background and doesn't require any more input - it shouldn't slow your computer down either, so you can just forget it's even there.
Don't make the mistake I did and wait to use FTP - you'll notice the difference as soon as you start.