Service businesses get a booking page without per-booking commissions or monthly SaaS fees from Easy!Appointments, the self-hosted appointment scheduler. Customers pick a service, provider, and open time slot from a clean web form; the system enforces working plans, breaks, and booking rules you define per provider, then confirms by email to both sides. The structure fits real service organizations: multiple providers with individual schedules, multiple service types with their own durations and prices, and admin/secretary roles for front-desk management. Two-way Google Calendar synchronization keeps each provider's external calendar authoritative - book in Easy!Appointments and it appears in Google Calendar, block time in Google and the slot disappears from the booking form. Version 1.6 adds SMS notifications and payment support, and a REST API opens the scheduling data to custom integrations. Built on PHP (CodeIgniter) with MySQL, it installs in a single folder and can share a database with your existing site; a WordPress plugin embeds the booking form directly in pages or posts. The interface ships in dozens of languages with time-zone handling throughout. GPL-3.0 licensed and free for commercial use - a helpdesk, clinic, salon, or consultancy runs its whole booking workflow on its own server.

A deliberately simple ticketing system standing in for both Zendesk and Jira: Peppermint handles internal staff requests and external customer support alike. The stack is modern full-stack TypeScript: Next.js and React over Prisma and PostgreSQL, which makes it light to run and approachable for developers extending it. Ticket creation is straightforward - a markdown editor with file uploads, assignment, status tracking, and a logical workflow that new agents grasp without a manual. Mailbox integration converts email into tickets automatically: configure SMTP/IMAP per mailbox and incoming messages become trackable tickets. Each client accumulates an interaction history, giving agents context on every past request before replying. Two touches distinguish it from bare-bones ticketing: a built-in markdown notebook with todo lists for internal documentation and knowledge sharing, and OIDC authentication so agents sign in through your existing identity provider - Keycloak, Okta, Authentik, or Azure AD. Configurable webhooks and email notifications push ticket events to third-party services. The UI is responsive from mobile to 4K, and everything works fully offline in air-gapped environments. Docker-native and scalable via Kubernetes, with an active community of 3,000+ GitHub stargazers.

Among open-source Mailchimp alternatives, Keila has the most modern UI - built in Germany on Elixir and Phoenix (the PETAL stack), with GDPR-conscious defaults including an optional no-tracking mode, and 100% open source with no proprietary premium tier. Campaign authoring is flexible three ways: a visual block editor with multi-column layouts, Markdown with or without WYSIWYG for hybrid HTML-plus-plain- text sends, and raw MJML for hand-coded designs. The personalization system is unusually clean - every contact carries custom data as a single JSON object (populated from sign-up form fields or pushed from your CMS/CRM), and Shopify's Liquid template language renders it into fully dynamic emails. Targeting uses a visual segment editor backed by a powerful segment language for complex logic over tags, language preferences, and any custom field. Sign-up forms with custom fields grow your lists; open and click tracking measures campaigns; scheduled sending handles timing. Delivery pipes through your own SMTP or first-class integrations with AWS SES (including automated bounce handling), SendGrid, Mailgun, and Postmark. A full REST API manages contacts, campaigns, and segments, with Erlang/OTP reliability underneath. Comfortable at 100K+ subscribers. AGPL-licensed, EU-hosted project, actively developed.

Feature requests, bug reports, upvotes, and a public roadmap: Astuto (Ruby on Rails backend, React frontend) gives users a Canny-style feedback portal so product decisions rest on visible demand rather than the loudest voice in the room. Feedback organizes into as many boards as you want (features, bugs, integrations), each post carrying a custom status you define - "planned," "in progress," "shipped," or whatever matches your process - and those statuses feed a public roadmap view showing users what is actually being worked on. Participation friction is adjustable at both ends: sign-in works with plain email or any OAuth2 provider, anonymous feedback can be enabled for unregistered users, and a moderation queue lets you approve posts before they appear when spam is a concern. Integration hooks are practical rather than sprawling - webhooks fire on events to connect Jira, Trello, or Slack, and a REST API manages the whole feedback space programmatically. Brand customization, an invitation system, private-site settings, and recap emails for administrators complete a deliberately minimal tool: it collects, organizes, and prioritizes feedback well, for free, forever.

Stop building internal tools and ship your actual product - Motor Admin exists for exactly that. Point this Ruby/Vue application at a PostgreSQL, MySQL, MariaDB, or SQL Server database and it generates a complete CRUD admin panel from your schema in under a minute - search, filters, create, update, delete, all through a polished UI, with every customization done through in-app settings rather than a DSL or boilerplate code. What elevates it beyond CRUD generators is the business-intelligence half: write SQL queries (with variables) and render results as tables, numbers, line/bar/ pie charts, funnels, or markdown; organize reports into shared dashboards; and attach queries and dashboards directly to resource pages as tabs, so an order record shows its revenue history in place. Operations beyond CRUD are covered by custom actions and a WYSIWYG forms builder that posts to your existing REST or GraphQL APIs - send a refund, trigger an email, whatever your backend exposes. Email alerts deliver scheduled reports, Slack sends personalized report alerts, and intelligence search spans all resources. Governance is included: role-based permissions with row- and column-level control (CanCanCan), an audit log of admin activity, multiple database connections, and configuration sync between staging and production. Mobile-optimized, AGPL-licensed, also available as a Rails engine.