The OpenOBEX Project is the foundation for many interesting applications. Here is a list which should give you some impression on OpenOBEX usability and a quick start.
ObexFTP - transfer files to/from any OBEX enabled device (most likely mobiles)
ObexTool - nice gui frontend to ObexFTP
IrCp - transfer files via IrDA the OBEX way (OpenOBEX sample app.)
gObexFTP - prototype GTK ObexFTP Client (draft)
vfs-obexftp - prototype GNOME VFS Module (draft)
ObexFS - prototype FUSE based filesystem (draft)
There are many other projects concerning OBEX and mobile phone data transfer. Here are just some more recent ones.
MyT68 - theme your T68 (alpha)
t68tool - backup your T68 (alpha)
dku2_nokia - communicate from your PC to your Nokia mobile phone (has its own OBEX stack)