UPDATE: The official release of Arduino now includes a 64-bit version, I suggest you use that one.
After bemoaning the lack of a 64-bit version of the last few Arduino releases, and the subsequent hoops that had to be followed to make the 32-bit version work in Ubuntu, I finally decided to get off of my laurels and just build the thing. You can get the package here, or build your own following the directions after the break.
Here is a brief outline of how to build the package. This basically comes down to building the rxtx library and avrdude program in the 64-bit environment, copying them into the arduino source tree, then building the Arduino library itself using the 64-bit environment.
Navigate to some directory that you like and pull version 16 of the Arduino source code from SVN:
svn checkout http://arduino.googlecode.com/svn/tags/0016 arduino-release-16
Grab the arduino-blessed version of avrdude and compile it:
wget http://www.arduino.cc/files/avrdude-5.4-arduino-src.tgz tar -xf avrdude-5.4-arduino-src.tgz cd avrdude-5-4-arduino ./configure make
Among other things, this should create the files avrdude and avrdude.conf. Copy them into the arduino source tree, overwriting the 32-bit versions:
cp avrdude avrdude.conf ../arduino-release-16/build/linux/dist/tools/ cd ..
Next, grab the latest binary release of the rxtx library and extract the serial library from it. The latest version fixes a problem that caused the Serial Monitor function to crash the program. It would probably be better to build this from source, however I ran into a bunch of issues with it and this was easier.
wget http://rxtx.qbang.org/pub/rxtx/rxtx-2.2pre2-bins.zip unzip rxtx-2.2pre2-bins.zip cp rxtx-2.2pre2-bins/x86_64-unknown-linux-gnu/librxtxSerial.so arduino-release-16/build/linux/dist/lib/ cp rxtx-2.2pre2-bins/RXTXcomm.jar arduino-release-16/build/shared/lib/
Now, all that remains is to build the Arduino distribution, which will create a nice tarball package:
cd arduino-release-16/build/linux/ ./dist.sh cp arduino-0016.tgz ../../../arduino-0016-linux-amd64.tgz cd ../../../
Copy this wherever you would like and use like a regular Arduino package:
tar -xf arduino-0016-linux-amd64.tgz cd arduino-0016 ./arduino