MongoDB is an open-source document / NoSQL database. It is slowly gaining popularity as an alternative to relational database. More and more applications and websites are starting to use it as their main database. Similarly many hosting providers are also offering support for mongoDB hosting on their servers. Here is a compact list of MongoDB hosting providers.
Openshift by RedHat is another cloud hosting option for MongoDB based applications. OpenShift gives you options to deploy and run MongoDB applications using your favorite frameworks and databases. For testing and development they have a free plan ( upto 3 gears ), for upgraded application they have bronze ans silver plans costing upto 20$ per month. Visit OpenShift
WebFaction provides 512MB application memory, 100 GB memory space along with a 600GB bandwidth, though upgrade options are available. The pricing is $8.50/month (paid yearly) or $9.50/month (paid monthly) with 60-day money back guarantee. They support MongoDB with Python, Ruby & Perl and also provide support for other databases like MySql, PostgreSQL, SQLite and offers full SSH access. Visit WebFaction
AppFog offer options to use MongoDB and PostgreSQL etc with various other technologies ( PHP, Python, Ruby etc) and also offer a free plan. Their basic plan starts from $20 per month and they offer various features with their plans like One-click setup of MySQL, PostgreSQL, MongoDB, Redis and RabbitMQ services and Scalable architecture with built-in caching and load balancing. Visit AppFog