What JFK Coins Are Worth Keeping?

I'm assuming that we're talking about half dollars.

Not accounting for varieties and errors, things you should keep are:

1964 (first year of issue, 90% silver)
1965-1969 (40% silver)
1970 (40% silver, only in mint sets, struck only in Denver)
1987, 2002-present (only sold to collectors. Half dollars have not been struck for general circulation since '01)

Anything with an "S" mintmark dated 1968-present (will either be a proof or silver proof)

If you're finding really nice coins from various years, which is common (because they don't really circulate), consider starting a set of the nicest ones.

As you find better ones, keep replacing them.

The list I've written is by no means the only ones you should look for, wait for someone else to respond and discuss errors and varieties before tossing any back.

Happy Hunting!

EDIT: to the forum!

"There are really no rare regular-strike Kennedy half dollars. Values for most Kennedy half dollars are cheap, except for the prices of couple scarce coins and error coins, of which there many.

The 1970-D Kennedy half dollar is the scarcest, worth about $20 in typical uncirculated grades.
The 1998-S silver matte finish Kennedy half dollar is worth $500.
All circulated copper-nickel clad half dollars without any errors are worth only face value.
Most proof Kennedy half dollars are valued between $3 and $10
Regular, uncirculated 1964 Kennedy half dollars are worth around $8.
Regular uncirculated 1965 through 1969 Kennedy half dollars have a value of around $5.
All worn silver Kennedy half dollars are worth right about whatever the current melt value is for the respective amount of silver"

http://coins.thefuntimesguide.com/2..._dollars.php

Silversearcher and aardspeed got it down pretty good.