It depends on what games you want to use the joysticks with.  The
Thrustmaster (WWW site at <http://www.thrustmaster.com>) is generally
considered to be the best joystick for flight simulators, but it's rather
pricey, and it's not ideal for other games.  The Thrustmaster is reportedly
also virtually unusable for left-handed people, as it is molded to be held
in the right hand.  Thrustmaster offers a Flight Control System, a Weapons
Control System, and rudder pedals; you must have the FCS to use the WCS
or rudder pedals.

The Gravis MouseStick II has some problems, but it works well with many
games, it allows a second joystick to be chained up, and it's considerably
cheaper.  Gravis (WWW site at <http://www.gravis.com>) also makes the 
Gravis GamePad, a lightweight, plastic Sega Genesis-style controller 
with an optional screw-in joystick adapter.  Like the MouseStick, it's 
inexpensive and allows chaining of ADB devices, and it can be used by 
left-handed players.

The Flightstick Pro is also popular and less expensive than the 
Thrustmaster.  CH Products (WWW site at <http://www.chproducts.com>), 
which makes the Flightstick Pro, also produces the Jetstick, an 
inexpensive but sturdy 2-button joystick.  CH will soon be releasing an 
F-16 Flightstick, Throttle, and rudder/driving pedals for the Mac.

If you have Sega Genesis, 3DO, or Atari joysticks lying around, you may want
to consider the Choicestick (WWW site at <http://www.kernel.com>), an
adapter that allows you to use control pads from certain other game
systems with your Mac.  You can purchase it bundled with a control pad
or joystick if you don't already own one.

Similarly, if you have an Commodore/Atari compatible joystick, the MacEnjoy
adaptor from Fesh! (thebug@berlin.snafu.de) will let you use it with your
Mac.  MacEnjoy also makes the MacEnjoy Style, a 5-button joystick molded
for a right-hand grip; it allows a second joystick to be chained up.

For current prices and pictures of most of these products, try the
Cyberian Outpost web site at <http://www.cybout.com>.