Andrea Vedaldi from University of California wrote a SIFT mex library for Matlab he has included the linux builds on his site but is missing the Windows therefore I have compiled up the 32 bit version for Windows. See the files below to download.
To download the linux and learn about the method used see:
http://www.vlfeat.org/~vedaldi/code/sift.html
Disclaimer
I have not made any fundamental changes to the original code except some small compile errors, this is being distributed under the same license as sourced on the Internet.
Copyright
This software program is Copyright © 2006 The Regents of the University of California and can be freely used for academic purposes (see the included license file for details). Although this implementation is original (in particular, it is not derived from Lowe's implementation), the SIFT algorithm has been issued a patent. Thus you should note that:
This software embodies a method for which the following patent has been issued: "Method and apparatus for identifying scale invariant features in an image and use of same for locating an object in an image," David G. Lowe, US Patent 6,711,293 (March 23, 2004). Provisional application filed March 8, 1999. Asignee: The University of British Columbia.
Guidance on Use
To use these files you will need to download the original version from the above site, then add these files into the folder so when Matlab looks for the windows mex files it is able to find them.
Files Provided
Below there are two download options, there is a zip file containing the collection of files click to download and also the individual files available for download, just click Single Files folder and then download them individually. If you have any problems please contact me.