I use UnFreez
http://www.whitsoftdev.com/unfreez/
Downfalls:
*Your images must be in .gif. (if your images are .jpg you'll have to convert to .gif before this program will join the images).
*I still use Adobe ImageReady to customize the playtime for each frame and optimize compression.
But this program saves a lot of time in ImageReady or creates basic gif animations...