When I want to use accented letters in PowerPoint 2007, such as a small "o" with a tilde, I usually go to the Insert tab on the Ribbon, and in the Text section click the Symbol button to get access to many Unicode characters.
If the Language Settings Tool is installed when Office 2007 is installed, some language options are available. For example, I can change the Language Settings in PowerPoint by clicking on the Office Button in the upper left of the screen, selecting Popular in the list on the left, and then where it says "choose the languages you want to use with Microsoft Office," clicking the Language Settings button.
For doing spell-check in another language, I can select the text I want to check, click the Review tab in the Ribbon, and in the Proofing section click the Language button to mark the selected text as another language.
I also like to use PowerPoint 2007 when I want to create a lot of slides with pictures in them. There are some cool things you can do with graphics (such as 3-D Rotation) in this program.