Magic Healing:
Go to a area that is safe from combat (Not in combat or in a room) and pause and go to the map screen. Now hit the X button to jump back to the Ebon Hawk and be healed. Select Map again and hit X again to go back to where you where.

Party Member Locations:
Bastila - Jedi Human - Taris
Canderous - Mandalorian Soldier - Taris
Carth - Human Soldier - Endar Spire
HK-47 - Combat Droid - Tatooine (buy him in the droid shop)
Jolee Bindo - Jedi Human - Kashyyyk
Juhani - Jedi Guardian - Dantooine (don't kill her!)
Mission - Tw'lek Scoundrel - Taris
Zaalbar - Wookie Scout - Taris
T3-M4 - Expert Droid - Taris

New clothes:
Equip a character with Dark Jedi Robes or Tusken Raider garbs then select the armor option of none exit then look at the new undergarments

Hidden Ending
(Note: You need two controllers for this trick)
With your primary controller plugged into ports 1, 2 or 3 have a second controller plugged into port 4. Before you enter the final battle with Darth Malak (do NOT open the door), pull both the 'L' and 'R' buttons on both controllers for a secret ending.

Keep the Sith Armor
Once you obtain the armor and complete the associated quest, equip it to another party member when you select the option of handing it over.

Keep the Sandpeople Robes
Once you obtain the robes and complete the associated quest, equip it to another party member when you select the option of handing it over.

Easy Path to the Dark Side
When you discover the stowaway aboard the Ebon Hawk, select the option Get out of here, whoever you are! Right now!! Then, before she leaves, talk to here again and select the same option. Continue to repeat as you gain 1 Dark Side point each time.

Fun with Bastila's Wardrobe
Equip Bastila with dark robes and then remove them to see her in slightly different underwear.