Artrage isn't a web tools as such but it's so good I just have to keep it on
the site. It's a lovely drawing program where you can select paintbrushes,
colours and have a go at bringing out the artist in yourself or
Something like this would be brilliant on an iPad. Whilst I know
there are other programmes that will do much more this has a certain
delightful character and is so easy to use. There is a free version
but I don't know how much longer for. Enjoy it while you can!