Pluto Puzzles - Fifteen Up

A numero-logical challenge

23 April 2010: Eight new puzzles

Fifteen Up. It's the new Sudoku. And it's taking the world by storm. OK, I made that bit up.
Unlike in Sudoku where the numbers could just as easily be letters or shapes or farm animals, Fifteen Up really does require you to do some arithmetic. Nothing complicated mind you, just enough to impress your friends.
The rules of Fifteen Up are simple. The challenge is to divide the grid into 15 regions, with the numbers in each region totalling 15.
The regions can be any shape, so long as the sum of the numbers in each region is 15. All the numbers are used; there won't be any gaps or disjoint regions in the completed puzzle.

This is what an unsolved Fifteen Up puzzle looks like:

When it's solved, it looks like this:

Puzzles 17-20 NEW! 23 April 2010

Puzzles 21-24 NEW! 23 April 2010

So there you go. Fifteen up. Pretty self-explanatory really, but be warned, it's not as easy as it looks at home.
Now it's your turn. Here are two dozen Fifteen Ups, in a nice printy PDF format, for you to get your teeth into:

Fifteen Up replaced an earlier puzzle of mine, called simply Fifteen. This version required all the regions to be squares and rectangles, and was probably a bit too easy! You can still see the old Fifteen puzzles here.