The "number of the Beast" (666) can be derived in eight different ways by placing + and - signs in the sequence 123456789. Only plus and minus signs may be used, and the numbers have to stay in that order.
To me, the most remarkable solution is this one:
+123 +456 +78 +9There are five solutions that include the number 678, such as:
-1 +2 -3 +4 -5 +678 -9And two solutions that use 567 as a component.
I'll defer posting those, to allow those of you who enjoy math puzzles to post your discoveries in the comments. (btw, there are also five solutions using the descending order 987654321).
Update: Rob from Amersfoort has posted the other answers in the comments.