As corporate intranets and extranets evolve, more content is coming out of documents and are living in some other form such as lists, or as page content.  The shift to using page content to dissimenate information, and be stored as metadata, is particularly on the rise. This can pose a variety of challenges for the business, like how to manage branding assets within the rich text editor and to make it easier for users to submit content....but that topic is for another day.  A frustration my current client recently voiced was that their content publishers were (dutifully) using the spell checker in the traditional "Page Content" field within publishing pages, but terms such as their company name, and some of their company lingo, were coming back as a misspelling.  My client actually sleuthed out the answer on this one, props to him....I love that I have taught my clients "how to fish".  :)

Alright - so how do we add custom terms to the dictionary in SharePoint?  It's surprisingly simple. 

In the case of Rightpoint, our company name is considered misspelled, as is the name of our intranet "iPoint".

To resolve:

1.  Create a text file on your local machine and add each custom term on a seperate line, save the file as "Custom Dictionary.txt"

2.  Create a library within the root of the site collection, call it "Spelling"; upload your "Custom Dictionary.txt" file to the library

Voila.  Done.  No more misspellings. 

Enjoy!