Here are tasks that can be done as well as some tips....
You can help improve the articles listed below! This list updates frequently, so check back here for more tasks to try. (See Wikipedia:Maintenance or the Task Center for further information.)
A dummy edit is a slight change in an article's wikitext that has no effect on the rendered page but allows you to save a useful edit summary. This is like a SMS (Short Message Service).
To make a "dummy edit" just make a slight non-rendering change to the page, fill out the edit summary with your short message including this tag: [[WP:dummy edit]] (include the four square brackets), and save your change. (Note that a null edit does not modify the wikitext and does not allow you to leave an edit summary.)
Wikipedia uses the Ogg Vorbis, FLAC and WAV formats for audio, as they are not encumbered by patents (an issue that prompted the decision that MP3 files will not be hosted at Wikipedia). Software supporting Vorbis exists for many platforms...
Various online tools (such as Zamzar) are available which let you freely convert one file format into another, and can be useful when you want to upload a file to Wikipedia.