Quote flipper

One of the most tedious coding tasks is to pick over a string converting " to ' (or vice versa). This does that for you.

Result:

Postage composer

You know how much the postage is, but all you have is books of 1^st and 2^nd class stamps. Enter the amount and let the electric imps find the least wasteful combo...

This venerable tool is still available on iliff.co.uk.