Installation Inkscape & Sozi in Ubuntu11.04
Inkscape is available in Ubuntu Software Center. Less troublesome to update all the related library. And add in Sozi extensions as specified in the page would do. Start your Sozi!
Installation Inkscape & Sozi in Windows 7 (should be similar to other Windows versions)
In Sozi homepage, there are all steps to install it in Windows 7 properly (http://sozi.baierouge.fr/wiki/en:install). Additionally to Inkscape, you need to be aware about installing both Python 2.6 + PyGTK 32-bit versions. Moreover, it is very important to choose the "all-in-one" PyGTK installer for Python 2.6. Otherwise, even though Sozi is available as an Inkscape extension, errors will appear (e.g. ImportError: No module named pygtk).
You can find a lot of figures at OpenClipart which holds a great collection of vector-graphic Public Domain caliparts.
Convert objects to path before visualizing the presentation in the browser. It can be done in Inkscape by selecting all objects and then pressing Ctrl+Shift+C. However, you should undo it to be able to edit the texts.
Presentations are about figures and talking. Do not use texts, but some words. If you put texts, people read instead of paying attention to you.
Just tell your story
Linking ideas is hard and demand great effort when creating slides and presenting them. Telling a story is more suitable for talking about your subject, it is more natural.
At the beginning, you may face a common issue that is using Inkscape and Sozi to create slides since you may be not used to it. That's not the point, trying drawing in a paper the story you have to tell as you'd have a friend besides you and listening to you. Then draw it at Inkscape and tell your story waving over the drawing in a browser.
Avoid using low-contrast colors, thin lines, tiny texts and small figures. Remember that you will (probably) expose it with a projector, so people in the end of the room (or even just in front of it) may not see texts or figures or even might not see the presentation just because there is no contrast between the colors you chose.
It doesn't matter the colors you choose, just be sure to always have a contrast between the line or text and the background. E.g., yellow/white, brown/black are a very bad choice, but yellow/black, black/white are good ones. Actually, it depends on how dark and how light the colors are, so they should be very dark and very light.
Last, if you can, test the presentation by using a projector before. Monitors are usually much more better (brighter) which can be tricky.
Vector graphics rules
As we can zoom in/out the presentation, avoid using non-vector graphics like bitmap. Besides it is not good for zooming in, it will significantly increase your SVG file size.
Avoid using heavy gradients because they slow down your presentation movements thus loosing smoothness.