The following U.S. organizations provide services to Koha or Evergreen customers (or hope to be soon)

Alpha-G (http://www.alphagconsulting.com/)

• Services offered: Data extraction, development, migration, support, implementation, hosting
• Services provided for Evergreen: data extraction 

Backstage Library Works (http://www.bslw.com/migration/)

• Services offered: Data clean-up, migration (with Alpha-G)
• Services provided for Evergreen: Data clean-up 

ByWater Solutions (http://bywatersolutions.com/)

• Services offered: Migration, implementation, support, hosting, training.
• Services provided for Evergreen: Installation, migration 
• Services provided for Koha: Installation, hosting, migration, support, migration, installation and configuration, training.

Cherry Hill Company (http://chillco.com/)

• Services offered: Installation, hosting, custom development.

Equinox Software, Inc. (http://esilibrary.com/)

• Services offered: Development, migration, implementation, support, hosting, training.
• Services provided for Evergreen: Development, migration, implementation, support, hosting, training.
• Services provided for Koha: data migration, hosting, support.

Libdata (http://www.libdata.com/)

• Services offered:  Installation, hosting, support, training, migration.

LYRASIS (http://www.lyrasis.org/)

• Services in the works: Support, implementation, hosting, migration, training, development.