Thunderbird is a total redesign of the Mozilla mail component to produce a cross-platform, stand-alone mail application using the XUL user interface language. It has many new features, among them the ability to customize your toolbars the way you want them. a new look and feel with a large number of downloadable themes which alter the appearance of the client, and the ability to add UI extensions.
eSpeak for Android is a port of the eSpeak Text-to-Speech synthesiser to Android, supporting 75 languages and accents. It is based on the eyes-free version, but with improved language selection and language name display, support for accents and special characters, improved handling of speech rate and pitch, support for MIPS-based devices, and improved support for SSML.
ViziSolve solves math problems. It does this by going one step at a time, highlighting each part as it is being used for the next line, and stating what it is doing at each step. Right now, it can solve most common algebra I level problems (not including graphing or word problems), and it may make a mistake once in a while. It runs on the Web.