What is the best way to create a powerpoint if I dont have MS office?
MS Office is not only the office suite. OpenOffice Org is a popular open source office suite, which means it's for free ! It allows you to do same tasks, as you would in MS Office. Services like Google Docs allow you to create office sheets online.
You can download a trial version of Office from the MS site. If you need to do a basic PPT, OpenOffice will do basic presentation files, as will Google docs (as mentioned by electrosam).Another alternative you might look at for creating presentations is http://prezi.com - lets you build zooming presentations that you control and can be accessed via the web.If you have access to Microsoft's SkyDrive (requires a Window's Live ID), you can even use the online webapps created by Microsoft. LMK if you want links on that option.
Try Zoho: http://show.zoho.com/login.do
You can use some free alternative as OpenOffice.org or some web based solution as Google Documents. These can actually export your document in ppt (MS PowerPoint) format.
That would be via Zoho.com If you have the Mozilla Firefox browser you can even add an extension in to create Powerpoints or automatically open up MS documents and excel files via Zoho.