I see John Freeman asked abut TablEdit back in September. I've been using it for a couple of years, and it's got my recommendation. You can "import" midi files and it converts them to staff notation and tab; you can change the key (I think!), and it's easy to edit tabs, or even enter them completely by hand. Yes, it costs a few bob, but it's good value for money. You can use it for a surprising number of instruments, including melodeon and whistle!

You can copy a midi from a web page by right-clicking the player image and following the menu commands.

Steve