If/when I can be bothered I shall post 3 apps of android a day which I currently or used to use. Feel free to add some for WinMo or alternatives :)
Right! down to business..
Unit converter, small sized app, I haven't really used it much but when I do its SUCH a useful thing to carry around, converts anything and everything with an SI unit. Occasional updates more for UI purposes than anything else now so its pretty much set in stone. Excellent one to carry in your pocket.