MS is opening up their development labs in a one-off experiment - July 23rd, 24th, and 25th. If you are developing a Silverlight product that you need some expert help with and can make it out to Redmond, they are allowing up to 4 people per company. Read more about it and sign up for it here.
I am surprised that there isn't an "Office-wide" setting for disabling spell checking and grammar checking but apparently there isn't. Hopefully with the drive towards making Office a "system", the next version will have some generic options that apply across all programs more than just the few that are available now in Office 2007.
With that said, if you are curious how to disable spelling checking and grammar checking in:
OneNote 200x, Outlook 200x, PowerPoint 200x, Publisher 200x, Word 200x, Visio 200x, InfoPath 200x, and SharePoint Designer 200x, read about it here.