Mergefly - A modern UI for GitHub pull requests
CodeStream - CodeStream helps development teams resolve issues faster, and improve code quality by streamlining code reviews inside your IDE
PullRequest.com - Code review as a service
Refactor.io - Share your code instantly for refactoring and code review
Codementor - “Instant help from expert developers. Codementor is your instant 1:1 expert mentor helping you in real time.”
Codacy - Automatically reviews code style, security, duplication, complexity, and coverage on every change while tracking code quality throughout your sprints.