I'm flying in to New York in a couple of weeks and would appreciate
recommendations for reliable inexpensive car service from JFK into
Manhattan.

Taxis charge a flat rate of $45 plus toll+tip from JFK to anywhere
in Manhattan. Carmel is a popular car service and will charge about
the same http://www.carmellimo.com/

If you want to get there faster and pay less, take the JFK Airtran
to Jamaica and the LIRR train to Penn Station, and then a taxi or
the subway from there.

R's,
John