Want to do us a favour? The following is a list of ways in which you can help out here at Roller Coaster Wiki. Also, there will always be some very short articles that you can expand.
Easy
These tasks are relatively easy to do, but may be incredibly tedious.
Adding {{trains}} template to articles
August 2014 - The {{Trains}} template can be easily added to articles and filled out using information from the RCDB.
Medium
These tasks take a little more knowledge of the wiki to carry out.
Replace article infoboxes
November 24, 2012 - Hundreds of roller coaster articles still have the old infobox. You can convert one to the new infobox by clicking on the + symbol beside the edit tools in source mode. Copy the code into an article, and fill it in!
Hard
These tasks are hard, and time consuming.