"Other" is neither a file nor a folder. It is a category of storage, just as Audio, Movies, Photos, Apps and Backups are categories. This helpful categorization is new with Lion. Look at the pondini.org in the post above yours.
Why do I need Omnidisksweeper and why can't I simply view the contents of the "Other" folder? Seems strange I need to pay to view my folders.
OmniDiskSweeper is free.