Your naming convention for ant targets should be very similar to the naming convention for Java methods: namely, simple and descriptive of what the target does.
Here's an excerpt from the Sun standard for method naming:
Naming a Method
Although a method name
can be any legal identifier, code
conventions restrict method names. By
convention, method names should be a
verb in lowercase or a multi-word name
that begins with a verb in lowercase,
followed by adjectives, nouns, etc. In
multi-word names, the first letter of
each of the second and following words
should be capitalized. Here are some
examples:
run
runFast
getBackground
getFinalData
compareTo
setX
isEmpty
Probably the biggest difference is the style for ant targets, which should be all lower cased letters with words separated by dashes.
For example, the following targets seem appropriate to me:
run-all-tests
build
clean
test-and-release
deploy
run-code-coverage-metrics
In the end, try to use the same good judgment you use when naming methods. If your targets are clear, descriptive, and easy to understand, you are in good shape.
For more detailed information on the topic, check out The Elements of Ant Style on the Ant wiki.