Google Picasa desktop software is one of my favorite desktop image management tool. I also use it to upload my images to my Picasa album instantly from desktop. Picasa also introduced the face recognition technology sometime back.
Here is a cool tip which you can use to create collage from your photos quickly.
Open Picasa, select multiple images by holding CTRL and click on create photo collage at the top of it.
Watch this screenshots for more info :
You can change lots of settings here and fine tune your photo collage. One done click on create collage.
Now go and create collage of your friends and stick it on your facebook wall.