Annotaion software.

I am just wondering if anyone is using annotation software on there computer.  I am looking for a good one but I haven't found any yet.  I know most of my Chinese friends have the English to Chinese software and it makes reading websites and documents much faster and more convenient.  When you don't understand one word in a sentence rather than having to look it up just being able to drag your mouse over it makes life so much easier.  You also don't loose the flow of the article.  I was using Dimsum's website annotator but it can be clumus to have to copy the website add in ever time.  Any ideas?