Barron's Dictionary of Accounting Terms has the following:

Provision
1 amount of expense that must be recognized currently when the exact amount of that expense is uncertain. At example is an expense such as a provision for income taxes.

2 contra asset account such as allowance for bad debts and allowance to reduce securities from cost to market value.

3 making an appropriation of retained earnings for a specific purpose.


Reserve
1 appropriation of retained earnings for a designated purpose, such as a plant expansion or a bond sinking fund. The purpose of the reserve is to tell stockholders and creditors that part of retained earnings is unavailable for dividends.

2 accrued liability, such as reserve for taxes (outdated usage).

3 Contra account to the gross cost of an asset to arrive at the net amount, such as reserve for depreciation or reserve for bad debts. In this use, the term reserve is outdated; accumulated depreciation and allowance for dates are used instead.

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Note added at 1 day1 hr (2006-09-30 09:56:05 GMT)
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David: Don't worry about being "out of date" - the main thing is being prepared to learn all the time :-)