Please recommend a tool to draw structs / classes and pointers

its a webapp.. but i tend to use ASCIIflow. dead simple and you can paste it anywhere

            +---------------------------+            +--------------------------+
            |Answer question            |            | ????                     |
            |---------------------------|            |--------------------------|
            | eat pizza                 |            | ????                     |
            |                           |+---------->|                          |
            |                           |            |                          |
            |                           |            |                          |
            |                           |            |                          |
            |                           |            |                          |
            |                           |            |                          |
            +---------------------------+            +---------+----------------+
                                                               |
                   +-------------------------+                 |
                   | PROFIT!                 |                 |
                   |-------------------------|                 |
                   |                         |                 |
                   |                         |-----------------+
                   |                         |
                   |                         |
                   |                         |
                   |                         |
                   +-------------------------+

A popular choice for this is Dia. Not only is it free and open-source, it's cross-platform, supports UML diagrams (click me for some examples), and has a variety of additional libraries and shapes that you can find for free. You can also export your drawings in a variety of formats - even lossless and vector.

You can get Dia here for Windows, or here for Linux

What you need is a UML tool. Some are incorporated into your IDEs .
Check this Wikipedia entry for a list of available tools.

You can try the yEd, which can also be started from a browser:

yEd is a powerful diagram editor that can be used to quickly and effectively generate high-quality drawings of diagrams.

Create your diagrams manually or import your external data for analysis and auto-magically arrange even large data sets by just pressing a button.

yEd is freely available and runs on all major platforms: Windows, Unix/Linux, and Mac OS.

You might also take a look at Visual Paradigm (Windows only). There is a free community edition available.