Any of you have any experience making a photo collage that you can save as a jpg or bmp file.

I'm trying to come up with a way to take 20 or 30 small photos and put them all together even slightly overlapping each other and at different degrees of rotation and then saving it as a picture.

I'm not sure any program I have is capable of doing this. I'd like to download something that is free to use as this will likely only get used a time or 2 for a special project. Just wondering if any of you have any experience with doing this ? and what program you use to accomplish this.