Here is a collection of source code available for the AP26 project on PrimeGrid.
I have posted my SSE and SSE2 modifications and also mirrored the original program source by Jaroslaw Wroblewski and Geoffrey Reynolds.
You can also read how the algorithm works.
My SSE/SSE2 code was compiled as C++ on Linux to link with the BOINC libraries. Changes will have to be made to compile on other platforms.
Jaroslaw Wroblewski - How the AP26 search works
Jaroslaw Wroblewski - Original AP26 source code
Geoffrey Reynolds - March 2009 BOINC modified source code
faster32 source code for 32-bit
faster IF.H source code for 32-bit
My 32-bit Linux C/SSE/SSE2 source code
My 32-bit Windows C/SSE/SSE2 source code
My 64-bit Linux SSE2 source code
Geoffrey Reynolds - generic PrimeQ using only long long ints
PrimeGrid's official homepage