fastSTRUCTURE is 2 orders of magnitude faster than structure. For everyone who has waited for structure to run this should make you happy.
Preprint of the manuscript describing it here: http://biorxiv.org/content/early/2013/12/02/001073

UPDATE comparison: Structure_v_FastStructure Structure (top) 8 days and counting FastStructure (below) 15 minutes. You can see the are nearly identical. I would expect them to be within the amount of variation you normally see on structure runs. Structure is only on K=4 (with 50,000 burnin and 100,000 reps and 5 reps of each K) where FastStructure took just under 15 minutes to go K of 1 to 10. Note: these are sorted by Q values not by individuals so, although I think it is highly unlikely, they may be discordant on an individual scale.

UPDATE on speed: ~400 individuals by ~4000 SNPs K=1 to K=10 in just under 15 minutes.

UPDATE on usage: Your structure input file must be labeled .str but in when you call the program leave the .str off. If you don’t adds it itself and will look for MySamples.str.str

It has a few dependencies which can make the installation a little intimidating. I found installing them was relatively easy and I downloaded everything, installed and tested it all in less than one hour.

The site to get fastSTRUCTURE:
http://rajanil.github.io/fastStructure/

You can follow along there, the instructions are pretty good. This is just what I did with a few notes.

At the top you can follow links to the dependencies.

Scipy + Cython

#Scipy
sudo apt-get install python-scipy python-sympy
#Cython
download + scp
tar -zxvf Cython-0.20.tar.gz
cd Cython-0.20/
make
sudo python setup.py install

Numpy

#probably the easiest way:
sudo apt-get install python-numpy python-nose

#what I did before I figured out above:
download + scp
tar -zxvf numpy-1.8.0.tar.gz
cd numpy-1.8.0
python setup.py build --fcompiler=gnu
#also installed "nose" similarly it is at least needed to run the test
#test
python -c 'import numpy; numpy.test()'

On to fastSTRUCTURE

wget --no-check-certificate https://github.com/rajanil/fastStructure/archive/master.tar.gz
#then
#check where GSL is
ls /usr/local/lib
# You should see a bunch of stuff starting with libgsl
# You can look in your LD_LIBRARY_PATH before adding that path
echo $LD_LIBRARY_PATH
# add it
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib
# check it worked
echo $LD_LIBRARY_PATH #mine only has ":/usr/local/lib" in it
#decompress the package
tar -zxvf master.tar.gz
cd fastStructure-master/vars/
python setup.py build_ext --inplace
cd ..
python setup.py build_ext --inplace
#test
python structure.py -K 3 --input=test/testdata --output=testoutput_simple --full --seed=100