We are in the process of replacing our Point to Point DDM-2000 OC-3 to T1 Add Drop multiplexers and I am having a hard time finding alternatives. Does anyone know of any manufacturers that they would recommend?

If it's equipment you can touch/replace, go with the Adtran Opti. You can do drop/add DS1's, DS3, ethernet, and a handful of other types. SONET side can go from OC3 to OC48. Good warranty and easy to configured (as far as sonet muxes go :-) )

the cisco 15454 and or turin are very good at this. adtran opti is a good option as well. i guess it comes down to what you are most comfortable using.