A site I came across some time ago, Try Ruby gives you an interactive (AJAX) ruby shell, with a simple tutorial to follow. In my opinion an awesome way to get started with a new language, I find learning is much easier by trying things out.
If you like this then you may also be interested in Try MongoDB (a similar MongoDB tutorial) and also codepad (a pastebin that allows you to execute certain programming languages and view the result).
Another nosql project, mongodb provides more than just key-value pair storage. It is a document orientated database (along the lines of relational databases, but without a fixed structure for tables, or relational queries). That is, you can store objects (documents) that contain any combination of fields and data (data being strings, numbers, arrays or objects themselves), and then perform queries on them.
I have been interested in using mongo as a logging system for Ircster for a while now (it supports large sets of data with full text search and very fast queries), however until recently there was no reasonable driver for node. There are now two drivers available node-mongodb (bindings to the C driver) and node-mongodb-native (a JS implementation of the driver). The native driver especially interests me as I can more easily understand and work with the code.