This site provides a free web application that lets users make their own, in their words, "emoticons, avatars and other custom icons from your own photos and pictures". 

Be aware that the end products are either png or gif format NOT ico as you may expect from the website's name.

Users can select from the following...

1.  
   This produces a 96 x 96 px png - image
   
    .
2. 
   This produces a 50 x 50 px gif - image
   
   .
3. 
   This produces a 19 x 19 px png - image
   
   .
4. 
   This produces a 48 x 48 px gif - image