I've had success using HTDP with students, and can recommend it - especially for the type of student that has interest/potential but that might otherwise struggle with a more standardized teaching approach.

I've also used Picturing Programs (http://picturingprograms.com/philosophy.html) and "How to Design Worlds" (http://world.cs.brown.edu/) with a few students that had a great deal of math anxiety and wanted a more graphics-intensive approach. I myself had/have a great deal of math anxiety, so I appreciate all of their efforts on this front. All of these materials help student's get their feet wet before they get too scared of the waves.

BTW, Does anyone know if someone has worked out the kinks so that you can use SICP examples directly in DrScheme/Racket to make the transition from HTDP to SICP easier for students? The last time I tried it, there were too many little gotchas and I gave up due to (volunteer work) time constraints.