Checkout this cool unit converter gadget with auto complete text box that I just submitted to google. It understands input as mathematical expression involving any combination of units (i.e. m/s^2 to km/hour^2 etc) so virtually any custom unit conversion can be done.

Will appreciate any feedback from the community.

Gadget location on Google: http://www.google.com/ig/add?moduleurl=http://www.myunitconverter.com/Module/UnitConv/DynamicUnitConvertor/Gadget/GadgetGoogle.xml

Gadget location on my website is: http://www.mycoolaids.com/Module/UnitConv/DynamicUnitConvertor/DynamicUnitConverter.aspx

and

http://www.mycoolaids.com/Module/UnitConv/SimpleUC/SimpleUC.aspx

The web site is still in kind of developing mode. I want to create a users supported website where units and the units related information can be added/deleted/edited by authorized users. As you would see, I have tried to tie any user input back to the given unit information page where more reference information (Wikipedia etc) can be found.