Tap to Talk is customizable. The voices can be turned on or off. You can also use it with text next to the images or turn the text off. This makes it a great app for students with different learning styles sharing the same device. Navigation is simple and no training would be needed. There are a handful of menus in this app.
iCommunicate is an inexpensive communication tool which allows users to create visual schedules, flashcards, and routines. You can use the words and images in their library of use your own images and voice. Most impressive is that you can customize your own images, to focus on the parts that are most functional to the child, such as the wheel on the bus (or the door), instead of the whole bus. There customer service is impressive. They responded to a tweet from me in record time. Consider this not only for children who need structure and predictability, but for those who have vision or hearing issues.
Expressive got a lot of attention at MacWorld 2011, and is flexible enough for a speech therapist to use with a student, or for a family who loves someone whose ability to communicate is temporarily impaired due to surgery or an accident. Barbara from SmartyEars was kind enough to donate this app for FETC 2011, to get it in the hands of educators who can use it.