Just to put it in context, it's for my son (11 - yes I know when I started allegro I was without babies....), who's artistic abilities are drawing stickmen in mspaint.
So, he wants to do some basic drawings (pixel not 3D) but also wants to have some ability to easily animate them, e.g. move them across the screen, etc so he can create some simple standalone videos.
Anyone recommend such free sofware, it's Windows btw.
A random search brought me Pencil, any good? simple to use?
When i was around 14 i played around with a shareware version of Moho and found it very intuitive to use.
Nowadays Moho has been replaced by Anime Studio [1] which should be just as good 
Not exactly free (50$) but you can try a demo
I'll check it out when I get home. Seems a tad complicated for him. Though motion studio looks a bit easier, but obviously depends really on what he wants to do with it.
At the minute it's just to create an animated intro to a youtube channel he wants to create....
BMP2AVI, is all he should need, maybe with a nice GUI, and a copy of GIMP/PAINT, IMHO.
It isn't free and not really pixel art in the traditional sense, but I've come to like Spriter. It has a software library that could be easily adapted for Allegro.
There's also Spine which appears somewhat similar.
Personally, I prefer to animate without manipulating individual pixels. Though if you're good at it, pixels are the way to go.
When I was 11, I used this:
http://www.iota.co.uk/tca/index.html
Pencil is good. Pencil is to Easytoon what Paint.net is to Mspaint.
Pencil is shit!
It crashes every 2 minutes, and when you draw a vector line as soon as you leave go of the stroke it draws something else in it's place. Doesn't even have any basic shape drawing tools, not much manipulation abilities, etc.
Everything so far is not free
You could teach him to create his own animation software, no?
Yes, I could, I could also devote my life to world peace or maybe become a tester for Firefox but I'd rather not and instead focus on stuff I want to do and let others do what they want (i.e. creating free awesome animation tools for me) 
[edit]I found synfig, which looks ok. There's also a few plugins for paint.net (or gimp as mentioned above) that seem to do about enough for basic stuff.
How did Synfig Studio work out for you? I'm looking at animation software myself.
I haven't fully tested it yet, but as you'd expect it's complicated 
Seem to do the same kind of job as Anime Studio, but for free and has a non-standard interface due to being cross-platform. Kind of a bit like Gimp and it's wierd menu system and non-mdi interface.
I'd just say avoid Pencil like the plague. If you want basic stuff then layers in paint.net/gimp/etc will do, otherwise something like synfig looks idea.
It does seem pretty robust... Have you managed to switch the UI to single-window mode (or "dock the windows"). Unlike Allegro, the online instructions aren't very clear.