The following companies offer professional support services for libsodium and applications using libsodium:

Edge Security (https://www.edgesecurity.com)

Libsodium-specific services include:

• Cryptographic and implementation auditing of libsodium usage.

• Security review of constructions, protocols, and applications using libsodium.

• Consulting on libsodium usage in applications -- web apps, backends, mobile,

  embedded, kernel, etc.

• General consulting and review of cryptography inquiries.

• Implementation security and helping to work toward a vulnerability-free

  codebase.

• Reverse engineering of complicated binaries.

• General consulting, advising, mentoring, and development.

Paragon Initiative Enterprises (https://paragonie.com)

Libsodium-specific services include:

• Library integration, with a focus on web applications (PHP, .NET, Python).

• Bespoke or standard high-level protocol design and implementation, e.g. Noise.

• Security audits, for in-house library integrations and/or high-level

  protocols.

• Custom application development that requires cryptography.

• Consulting and mentoring services.

(Please submit a pull request if you want your company added to that list)