Some of these require subscriptions but should work from within Warwick (or other institutions') networks.
The Palgrave Dictionary of Economics. A nice muti-volume collection of essays on major and minor economic topics, but vastly more functional in its online form.
The obvious Mathworld for basic definitions and so on.
Java tutorials and API reference. If you are going to program in Java (or indeed various other langauges for which a plugin exists) I recommend using the Eclipse IDE which thanks to clever autocompletion, refactoring and wizards makes Java's verbosity bearable.
For scientific programming it's worth considering (as an alternative to the pervasive Matlab) using Python with numpy/scipy/matplotlib which are all gathered together with many, many other useful tools in "Python for scientists" Python(x,y). I'm hoping to migrate towards Python where possible. If like me you are moving from Matlab the Matplotlib library may prove useful.
Mathjax for Latex style markup on the web.
Latex in Powerpoint 2007.
Everything you ever wanted to know about how to make coffee.
A collection of over 80 free pieces of software for Windows.
Downloadable files (a collection of things I've written that may be useful)
On the left navigation menu you can choose from some RSS feeds related to my work (albeit at a very general level).