on a side note: this is part of the HTML5 specification. If people are not afraid of Google/Chrome and if being online is not an issue, it's as simple as this: http://jsfiddle.net/dirkk0/pGFuR/
I only found https://wiki.mozilla.org/SpeechAPI for the FF implemenation, looks like it has no Linux support either, but I only glanced at the patch they made... It seems to support recording for OSX and Windows at least.