freevec.org

First you have to register to the site here (in time, we intent to offer OpenID support, so that there is no need to create a new account on the website).

Afterwards, you just have to Add a new function. You can multi-select the category your function/entry belongs to by clicking on the taxonomy terms.

Using the Chart API and our own CSV Chart Drupal modules, it's really easy to create and display beautiful Google Charts like the ones on the site. For help on how to enter the data, please read the CSV Chart module page.

Since we use the Geshi filter module, we can take advantage of its cool syntax highlighting features. Basically all you have to do is enclose your code with the [ code ][ /code ].

Using DruTeX and selecting the corresponding input format, you can use a LaTeX subset to do nice math in your text, etc. Have in mind, though, that it's not a full LaTeX environment. More can be seen in DruTeX documentation. You can see an example of using DruTeX module here.