For NoSQL fans, MongoDB is definitely the most popular solution with the simplicity and cross-platform support offered.

In order to manage MongoDB databases easily, Genghis, a single-file, self-hosted and web-based solution is pretty handy.

It can be installed either as a Ruby gem or as a standalone PHP script.

Genghis is capable of managing any number of databases on any number of servers with support for managing databases, collections and documents.

The interface of the application is responsive and works well down to mobile.

Forward is a fresh e-commerce application (that is in the alpha stage) built with PHP and using MongoDB for storing data.

The application is free, open source and built with developers in mind makes with easy custom coding, powerful templates and expressive syntax.

It has a REST-like API for interacting with every feature from orders to customers or products.

Thanks to MongoDB, the capabilities of the store is not limited to the default database schema and it is a breeze to have new fields/structures for everything.

Design of the storefront can be changed with a powerful templating engine (Smarty 3) and the backend is built with Bootstrap.

For anyone willing to share tweets when they are not online, various web services exist to accomplish this task (I had also built an open source app: Scheduled Tweets -not updated anymore-).

Tampon is a free and open source alternative (that is inspired from Buffer) that schedules tweets.

It is a Backbone.js application that uses MongoDB for storing the data and has a PHP-based REST API.

The application allows creating a schedule with multiple entries and auto-sends your tweets at those periods.

Tweets entered can be re-ordered with drag 'n' drops or, optionally tweeted instantly.

Considering it is open sourced, Tampon can also be a good starting point for creating a feature-rich, customized version.

When it comes to tracking websites, there are open source analytics apps like Piwik, OWA or ChiliStats. But, for mobile, it is hard to find a good one.

Countly is a modern, real-time and open source mobile analytics application which can collect data from mobile phones and visualize that info for analyzing mobile app usage + end-user behaviour.

It is formed of 3 parts: the Countly server + frontend, iOS SDK and Android SDK.

With an event-driven system, almost every action can be tracked including in-app purchases, when a user closes the app, ad-click behavior, etc.

All these details are displayed in the slick interface of Countly. And, you are not limited to racking a single app. The same interface enables adding any number of apps.

Ospriet is an open source web application, built by Twitter, that enables audiences to post and vote on questions/comments for talks, presentations, events, etc.

The application works with a dedicated Twitter account and anyone can send a question/comment by simply posting a @-reply to that account.

This tweet is then retweeted by Ospriet so that other users can see/favorite it and they will be presented as a list of most favorited entries in Ospriet's front-end.

It is built with Node.js, uses MongoDB for storing the data and uses Twitter's Bootstrap for the interface (which is responsive).

selfoss is an open source and lightweight web application that can fetch content from any number of sources.

RSS is the content type supported by default, however, with its plugin system, any new source types (log files, e-mails, etc.) can be implemented by adding a single class.

The application has a simple-yet-functional interface which also supports navigating via keyboard.

It is also flexible in means of the database used; you can either go with MySQL, SQLite or MongoDB.