Yes, Openoffice is a great tool but does not have every feature of powerpoint. You can also try google docs which works through the web, but once again there might be compatibility issues when transfering it.
You can also try using Prezi or using some Portable Apps, which allows you to open applications straight from a flash drive with no install required.
People can also try to save the files in multiple formats if its not too much trouble to help those with older software.