Duct tape can fix anything
C - one operation calculator

Let's have this for a start.
It's actually quite hard to find pieces of C programs that aren't whole programs. I had most trouble with declarations.

// http://stackoverflow.com/a/2911978 Block #1 (changed i to a)
static int a = 10;
// http://stackoverflow.com/a/2911978 Block #1 (changed i to b)
static int b = 10;
// http://stackoverflow.com/a/442647 Block #1 (changed c to op)
unsigned char op = (unsigned char)-1;
// http://stackoverflow.com/q/3711048 Inline block #1
int main()
// http://stackoverflow.com/a/14902422 Inline block #1
{
// http://stackoverflow.com/q/217074 Inline block #2 (changed i to a)
scanf("%d", &amp;a)
// http://stackoverflow.com/a/23353870 Inline block #2
;
// http://stackoverflow.com/q/217074 Block #2 (changed c to op)
scanf("%c", &amp;op)
// http://stackoverflow.com/a/23353870 Inline block #2
;
// http://stackoverflow.com/q/217074 Inline block #2 (changed i to b)
scanf("%d", &amp;b)
// http://stackoverflow.com/a/23353870 Inline block #2
;
// http://stackoverflow.com/a/4173188 Block #2
int result = 0;
result = (op == '*') ? a * b : result;
result = (op == '/') ? a / b : result;
result = (op == '+') ? a + b : result;
result = (op == '-') ? a - b : result;
printf("%d",result);
// http://stackoverflow.com/a/3245525 Block #2
printf("\n");  /* prints newline */
// http://stackoverflow.com/q/4138649 Inline block #1
return 0;
// http://stackoverflow.com/a/14902422 Inline block #2
}


Takes a simple integral operation like 3+151 or 41/2 on stdin and outputs the result to stdout.