Alright, I found a way to do this.
You can use an existing Fedora installation to create an Intel-Mac bootable USB drive.
I used VMWare Fusion to install a virtual Fedora 15 alpha system.
Then, attach the USB drive and make sure to connect it to the virtual machine (and not Mac OS X). VMware Fusion will give you this option, although I am sure the free VirtualBox software can do the same.
Now, follow these steps in the Fedora system:
# Go to Add software and install livecd-tools
# Search for livecd
# Now, start (Fedora's) Disk utility
# Format the USB drive, giving it a GUID Partition Table
# (so not Master Boot Record!!) and don't create any partitions; leave it empty
# We assume here the USB drive is at /dev/sdb
# Make sure it is (e.g. look in Fedora's Disk utility,
# it will display that info when selecting the USB drive in the menu)
# Start a Terminal (Applications > Utilities)
# Type 'su' and your password:
# Now start the script, assuming the Fedora live ISO is in your home directory
livecd-iso-to-disk --format --efi Fedora-15-Alpha-x86_64-Live-Desktop.iso /dev/sdb
Press ENTER every time the script asks for confirmation.
# That's it!
---------- Post added at 12:46 PM ---------- Previous post was at 12:11 PM ----------
By the way: Mac OS X will say it cannot read the Fedora Live USB drive, that's ok.
And on a more sad note: I haven't been able to actually *install* Fedora 15. The live system works fine, but I can either not boot after installing to the harddrive, or even the Anaconda installer crashes when selecting a Custom Partitioning layout.