What Are the Next Big Things In Open Source?

Last week, SDTimes compiled a list of the five next big things in open source. I'd like to hear what you think are the open source technologies to watch in 2011.

The SDTimes list includes technologies such as HBase and CouchDB, building on the NoSQL momentum. An interesting observation is that the addition of Eclipse Virgo to the already rich  Eclipse eco-system really adds weight to the runtime options available. According to the article, Windmill is poised to become a successor to Selenium in the web app testing arena. The project that might appeal to most Java developers is Gosu: 

Overall, Gosu is a compelling new Java scripting language, and a reasonable alternative to Ruby and Groovy.

Predicting the future is a difficult thing to do, but here are some things that I think will make it big in 2011: 

e4:

Eclipse has always had lots of cutting edge open source projects. If I was to take my pick of what will do well next year, it has to be e4. A new way to develop RCP applications, and under development for the last two years, I think this will really gain traction in 2011. 

UI Builders: 

Following on from Google's acquisition of Instantiations, and the subsequent open sourcing of the WindowBuilder tool, I think we'll see a big surge in UI builders for all different target platforms. Right now Swing, SWT and GWT are under control, but we could still do with a visual editor for Android (or iPhone) apps. 

Cross Compilation / DSLs

OK, nothing particularly new here. DSLs have been prevalent for quite some time now. But when I look at Xtext, and I see what they've already done with Applause, their mobile application DSL, it's clear to see that DSLs are the way forward for a single source approach for your applications. There's no doubt that mobile will continue to be big in 2011. DSLs (particular with the power of Xtext) are the perfect match for this trend.

This is far from an exaustive list, and barely scratches the surface of what may happen next year in open source. I'd really like to get your opinions. What have you used recently that looks like it will make it's big break in 2011?