As I have mentioned in previous posts, the key to technology in the classroom is making sure that assessment is possible with each tool. Otherwise, there is no way to tell whether or not the students are getting any value from the exercises.
For this reason, it is important to tie the technology to the objective. The students need to be able to easily see the connection between what is, admittedly, a novelty in the classroom and the TEKS behind it. Simply setting up stations because they will draw the attention of the students is the electronic equivalent of busywork.
We should also hold students accountable so that they understand that time with the technology is not "blow-off" time or an otherwise lighter portion of class where learning is suspended. The integration of technology into the classroom is heavily dependent on student interaction due to its editable and interactive nature. Students must understand that they should treat that time (although occasionally fun) with the same level of focus as lecture or tests.
I liked two of the sites, Interactivate and Mangahigh, because they presented functionalities that involved competition and measurement. One of the best ways to engage students is to create learning situations where they must strive to excel against one another (in a harmless and fun way, of course). Mangahigh's games would be especially effective for challenging students to improve their understanding in order to "win" the games.
As far as apps are concerned, Isoceles: the geometry sketchpad would be a very useful app for me in terms of creating instruments and assessments. One of the biggest problems I run into during tests and so forth are diagrams and models that are unclear. This app would allow me to draw far clearer pictures for my students to use.
I also like the Geometry app, because it would be a good supplementary aid for my students, particularly after I have taught a lesson. Teachers teach the same subject different ways, and having a second voice, even an electronic one, might improve a struggling student's comprehension of the concept, especially during homework or test review.
Students could also use the iPads or iPod Touches to photograph or download sections of my lessons. During this semester, many students asked me for permission to photograph sections of the ActivBoard or white board where I'd written a great deal of instructional material. I almost always agreed when asked, but expanding this function of the device even further might allow students who don't normally take notes in the classroom to retain a semblance of the knowledge for their future records and learning.
Hope this helps. Good luck in the classroom!