No, Impress (the OpenOffice presentation app) cannot display swf (Flash) files .
Personally if I was going for a Window$ portable machine I would not go for something with so little power as an eee. PC world are doing a 12" Advent for £350 (Core 2 Duo, 2GB etc.) - is that portable enough?
Oh forgot to answer your other question - it has a standard (non-HDMI) monitor connection, so it should connect OK to most projectors but the 900 will only display up to 1024x768 - the 901 might be more so check the specs.
Thanks for your answers - I am looking for something cheap and portable which boots fast, and can run Windoze software, especially powerpoint. The lenovo thinkpad looks ideal - apart from the price! The eee 901 looks like a possibility, but I am a little concerned with how low powered it is..... I will take a look at the advent machine.
If you want cheap, then buying a machine that doesn't mandate having either Windows or Office will be considerably cheaper. I hear good things of the eeepc for general day to day use. No need to buy Microsoft Office when you can get very similar functionality from either OpenOffice or Symphony as well as the ability to open, edit and save files in Powerpoint, Word, Excel format.