As a photographer, I often have the need to transfer large documents (mostly images) to my clients. I had considered an FTP site, but for economic reasons, I opted for a .Mac account (iDisk) to partially fulfill my business needs. Partially, because I'm limited to 250megs of storage and because the service is sometimes painfully slow.
Now I've found a way to transfer large documents to clients using the peer-to-peer (P2P) program LimeWire. I simply alpha-numerically rename the document or folder I want to send (using 12 to 14 characters), thus severely limiting the chance that other users would enable an exact search. For obvious security reasons, you might want to also compress and password encrypt your document or folder. I then manually place the document in my designated "shared" folder, and restart LimeWire.
The document now appears in LimeWire's library and is ready to be uploaded. I then notify my client that the document (bg507khf2bz87, for example) is available, and that he can search for it using his own P2P software and proceed to download. The advantages of this method are that the documents can be downloaded at the client's leisure as long as your sharing software is open; that downloads can be resumed at a later date; that because you only have two users sharing a document, the download speeds are quite fast; and best of all, it's free. I strongly believe in the future of file sharing software and its legal and unabided use.
[robg adds: There are obviously many ways to transfer a file from one user to another under OS X. Using a P2P app like LimeWire is a unique approach, assuming your machine stays awake and online much of the time.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050405160920368