I don't think one existed so here it is!
BTConvert. A portable currency converter for BTC, USD, EUR, GBP, AUD, Linden$, Pecunix, RUB, CAD and PLN. It takes the exchange rates from the internet every 30 minutes. Nothing fancy, it just works. I think...Click here to download it
AutoIt3 sources are included. If you don't need them just keep the executable.
Suggestions, tips etc are welcome as always.
Also if anybody has missed it I've made a portable wrapper for Bitcoin: http://bitcointalk.org/index.php?topic=944.0
Changes so far:
v1 Initial version.
v2 Added AUD.
Added refresh button.
v3 Some timers changed.
Added link to bitcoin.org when someone clicks on his label.
v4 Users that click refresh too often are asked if they are sure.
Added Linden dollar and Pecunix.
All labels are links to related pages.
v5 Changed Lindel dollar source.
Fixed a bug with manual refresh warning.
Limited the decimal digits to something sensible.
v6 Added RUB and CAD.
Fixed the LD label link.
No more beeps. Instead it will show a persistent message that something went wrong.
v7 Andrzej added PLN. Thanks for that Andrzej. :-)
Stores the last update time in the INI so that exiting and running the program soon won't cause an update.
v8 Docks in tray.
No longer asks if you refresh the rates very often.
v9 Support for the new Mt Gox ticker data.
v10 Fixed last version because it broke.
Data for most currencies is taken from: http://openexchangerates.org/latest.json
Changed BTC decimals to 4. (0.0001