putting arrows on pictures

[Roger Searle]

Hi, I am putting together some articles on a wiki, and including some 
screen shots on which I want to draw an arrow to point to a particular 
part of the screen.  I thought this would be a really simple task but am 
yet to find some cool tools to help with this.  I can use gimp to draw 3 
lines to make an arrow but really my drawing skills still suck badly as 
they have all my life. 

Does anyone know of a package that has a tool to draw arrows?  Or a 
method via gimp to draw a proper arrow?

Cheers,
Roger