I received a $10k signing bonus repayable upon voluntary termination
of employment prior to a year.  The company is exploring startegic
alternatives and will be sold within 6 months.  I have offered my
resignation and they have told me I owe back the entire pre-tax bonus.
 Is this fair? Any grounds for an appeal?

Sounds similar to what happen to someone I know.  Received bonus,
repayable upon voluntary termination, he quit prior to end date, he
hired an attorney and settled paying back half.  He should have lost
though.  They settle to avoid the hassle.  Good Luck.

Employment law is a very state specific issue.  The answer will depend
on the states involved.

However, if your contract says that you owe the money, why would you
think that you don't?  If you pay it back across a calendar year end,
you also raise interesting tax issues.