I wonder what are the applications that you use with students that make a difference for them? Here are some of the ones I use that students seem to enjoy.
Edmodo - terrific tool for managing a class in a "school sponsored bebo" (as one of my students called it) format. Nice functionality for handling assignments, polls etc. Students love it.
Voicethread - terrific tool for sharing all kinds of data from video to still images, with comments via a wide range of options.
Wikispaces - very easy way to get a web site up and running -the free ones for educators are a real bonus.
Google Apps - while very bandwidth hungry these tools offer great flexibility for collaboration and communication. Google Sites is the best aspect of this suite in my view.
Google Sketchup - what a fantastic 3D visualiser this is. A real favourite.
Delicious and Diigo - great tools - work well together.
iTunes - the best way of organising audio and video
Youtube - there is so much quality and education specific stuff that it is worth putting up all the rest of the rubbish that people want to share.
TED - you can always find really cool stuff here for use with students and staff.
Jing - screencasts and captures
Prezi - very cool presentation tool - makes an audience stay awake!
Aviary - awesome suite of online editing tools - students love Phoenix (photo editing) and Myna (Sony Acid lookalike) most.
Livebrush - very cool graphics program.
Google Earth - you can do so much with this great tool - always a favourite.
Pulse Smartpen from Livescribe - not a software tool per se, but a combo of a pen, microphone, camera and software. If only it had OCR ...