AKROBAT  I like the idea, however the Bonjour feature simply doesn't work.

The problem is that the only machine that shows up in Ubertragen is the same one I'm sending from, which doesn't make sense 'cause other apps can work fine over Bonjour.

I'll agree with HERVé 5. I also use DropCopy to send files... much easier. For Bluetooth I use the Apple's built in service.   
(Version 1.5.1)

KEDOS  AWESOME and lightweight utility! Very useful - it has almost completely replaced my ftp client. The bluetooth with my k800i doesn't work either, but I don't need it.

I don't know what the deal is with the name, though. I tell my friends that they need to go download "Ubagrabatabagibbin." What does it mean?  
(Version 1.5.1)

MSTAC  I must say that this widget is exactly what I was looking for. But for me it does not work... I'm only talking about the bluetooth mode. I'm using a macbook, and a SonyEricsson k800i. I can send files without problem using the "Bluetooth File Exchange" (from Apple), but Ubertragen gives me an error "A Bluetooth error has occured, is the device in range?". As there is not much configuring, I don't know what to do to solve this...

Any help warmly welcomed!  
(Version 1.5)

HERVé 5  This comes in addition to my previous comment (below). I must say, for ftp transfers, Ãœbertragen does rock. I find it way more efficient than the others in this "just drop" category.  
(Version 1.5)

HERVé 5  For more efficient local-oriented transfers you also have DropCopy, presented on MU at http://www.macupdate.com/info.php/id/16250 .

DropCopy doesn't do ftp but I find it more efficient ('less clicks') and it still supports internet IPs in addition to bonjour...  
(Version 1.5)

HENRIKTEKNIK  This is unbelievably indispensable. Ãœbertragen deserves 5 stars!  
(Version 1.1)

BASTIBENSE  AWESOME! 5 stars. Finally a quick way to send files between my machines without having to use a file server every time.  
(Version 1.1)

HENRIKTEKNIK  Really great. Thanks!  
(Version 1.0.2)

GEORGES ROBERT  This widget is really great, but I found a small bug when I had deleted a file I sent and then tried to empty the trash.

The last sent file is still open after the FTP transfer.

You can look at "Open files" when you double-click the widget into the Activity Monitor.  
(Version 1.0.1)

TROYKOELLING  This is the first non-Apple widget that I've seen that "gets it". It does one thing well (aside from some initial bugs), and it doesn't require any setup to get started. So please don't add more complex file structures :) I like how it is.   
(Version 1.0.1)