Motorola ATRIX HD, Motorola DROID RAZR M, Motorola DROID RAZR HD, Motorola DROID RAZR MAXX HD, Motorola ELECTRIFY 2 and the Motorola PHOTON Q 4G LTE. The older models that you need to trade include the Motorola DROID 3, Motorola DROID X2, Motorola ATRIX 4G, Motorola ATRIX 2, Motorola Admiral, Motorola CLIQ 2, Motorola MILESTONE 3, Motorola MILESTONE X2, Motorola ELECTRIFY, Motorola PHOTON 4G, Motorola XPRT, Motorola TITANIUM and the Motorola TRIUMPH.
You can get started by clicking on the sourcelink. While the offer is available in the U.S.only right now, Motorola did say it will roll out the program to other countries "over time". Motorola says that the $100 could be offered in the form of a Motorola pre-paid Visa card, a Verizon gift card, carrier credit or another equivalent.
Motorola has been criticized by owners of some of the phones eligible for the $100 trade-in offer. While it might be disappointing for owners of these models to be stuck on Android 2.3, it probably beats having to deal with a laggy, buggy Android 4.0.
source: Motorola via Phandroid
Motorola will give you $100 for any of these models, toward the purchase of a newer handset that supports Android 4.1