Google Translate Anywhere is available for Firefox and Chrome, and I believe for Opera as well.
Basically, it opens Google™ Translate in a frame (of a customizable size) straight over your page. You select a text, right-click to invoke a Context Menu, and choose the option. The extension captures text selection and allows to choose source/target languages, too.
Google™ Translate, in turn, has "listen" button (I highlighted it with red circles).
The integration with a ready-made service automatically provides with some nice features like remembering your recent requests in your Google account, and more.