I had some posts on brand extensions here before, and tried to categorize brand extension, but here are some excerpts of another interesting categorization by Mike Bawden of Brand Crafting”

The Next Step – An evolutionary brand extension.

The Sequel – More than evolutionary, these extensions tend to be a complete re-thinking of existing products and then re-packaged and represented with or without the lineage clarified.

The Spin-Off – Just as the name implies, these are extensions that take some small element of the original and tries to make a full-blown brand out of it.

The Partnership – Co-branded extensions can confuse and confound customers, eventually pissing them off in the process.

The Anti-Brand – Not really an extension, these are brands that leverage the brand awareness of another product to their benefit by claiming to NOT be them.

The Non-Sequitur – These are brand extensions that generate a “huh?” reaction out of consumers.

Read more on the subject, from Amazon.com:

Brand Extensions: Keys to success in international marketing

Brand Stretch: Why 1 in 2 extensions fail, and how to beat the odds: A brandgym workout