I have developed a driver for OpenOCD that supports the JLink USB interface. I have tested it on my JLink and an IAR AT91SAM7 kickstart board and it seems to be working well. Note that the JLink is only supported under Windows so Linux users are out of luck.
The patch for the OpenOCD sources is found here:
http://www.shumatech.com/files/jlink.patch
Since the JLink is only supported under Windows, you need to use Cygwin to patch and compile the OpenOCD sources. Make sure you have all of the requisite Cygwin packages installed (patch, svn, gcc, autoconf, etc.). You also need to copy the JLinkArm.dll from your JLink installation into the src/jtag directory.
For example:
$ svn co http://svn.berlios.de/svnroot/repos/openocd/trunk openocd
$ cd openocd
$ wget http://www.shumatech.com/files/jlink.patch
$ patch -p 0 < jlink.patch
$ cp /cygdrive/c/Program\ Files/SEGGER/JLinkARM_V360a/JLinkARM.dll src/jtag
$ ./bootstrap
$ ./configure --enable-jlink
$ make
Then add the following lines to your openocd.cfg:
interface jlink
jtag_speed 0
Note that the JTAG speed is given in kHz with 0 meaning to autodetect.
Enjoy!
-Scott