Write a Number as a Fibonacci Sum
GolfScript, 54 characters
~1.{3$)&lt;}{.@+}/&lt;[[]]{{+}+1$%+}@/\{~)+{+}*!}+,{'+'*n.}/

Test it online or have a look at the examples:
&gt; 54
2+5+13+34

&gt; 55
1+2+5+13+34

3+5+13+34

8+13+34

21+34

55