Ed. Note: If you love Gmail but just can't shake a longing for folder-style organisation this clever hack will help you create pseudo-folders.
Reader jrc03c came up with a great solution for mimicking folders in Gmail:
As a GMail user, I love the labels system, and cringe when I think about other older e-mail systems where you had to put messages in folders. The one major disadvantage I've found with labels, though, is the lack of sub-labels.
To remedy this, we can take advantage of the fact that GMail sorts labels alphabetically by adding a symbol to the beginning of labels. This creates makeshift categories. As you can see in the image here, I've added an asterisk to all of my work labels and coloured them green, added a double slash to personal diary-like labels and coloured them blue, and added a plus sign to my friend & enemy correspondence labels and coloured them red.
GMail sorts them alphabetically beneath the symbol, thus keeping related labels together. I hope this helps out some fellow GMail users!
Have some Gmail-fu of your own to share? Let's hear about it in the comments.