I googled and found these...some people also suggested using rubbing alcohol
there are a few tips here:
http://www.thriftyfun.com/tf67210823.tip.html
and from another page 3 other methods...
Iron on Paper Method
Step
1
Take a blank piece of paper and lay it flat. The paper should be large enough that it completely covers the iron-on transfer.
Step
2
Lay the piece of clothing on the paper. The iron-on transfer on the clothing should be face down on the paper.
Step
3
Iron on the back of the article. Keep ironing. This may take up to 5 minutes of ironing.
Step
4
Observe that the transfer has stayed on the paper.
Peel off Method
Step
1
Cover the iron-on transfer with a piece of a paper and reverse the material. Then iron onto the back of the shirt (assuming the transfer is on the chest) for about 90 seconds, or until you are sure that the transfer is extremely hot. At this point you can reverse the shirt and peel off the paper. The transfer should peel off with it.
Step
2
Reverse the article of clothing.
Step
3
Iron on the back of the shirt for a couple of minutes assuring the iron is on the highest setting.
Step
4
Peel the transfer off the shirt.
Iron Directly on Transfer Method
Step
1
Wet the iron-on transfer and area around the transfer.
Step
2
Iron directly on the iron-on transfer in circular motions with no paper between. The transfer will begin to melt into little balls.
Step
3
Use a lint brush to pick up the remaining melted balls of the transfer
just noticed someone else googled too!

NO BLAME HERE IF IT DOESN'T WORK...let us know, though. I Just threw away shirts before that I thought were beyond help...didn't think I could save them