Howdy, got bored on Wed. and started working on this. Its about finished, code still needs to be optimized, and a few things need to be prettied up (text & the little win/lose/indiferent icon on the header button), but it seems to work well other than that.
http://www.tiefight.com/flash/minesweeper.html
Obviously can't right-click, so shift-click will set your flags. Click on the middle button at the top to re-set the board. Click on the re-size button at the top (two arrows pointing away from each other) to change the dimensions/number of mines.
Enjoy ;)