These were posted at Planetgamecube. Haven't tried them yet, but all the other codes they've posted for this game have worked. If these are like the other codes, the ship and level they unlock, will be unlocked permanently, so don't use them if you want to earn them buy getting medals.

For the codes, go to the code menu, enter the top one, then the bottom one.

Unlock Slave I (Boba Fett's ship)

PZ?APBSY
IRONSHIP

Unlock Triumph of the Empire

AZTBOHII
OUTCAST!

Update

Both codes work, and they do unlock the ship and the level permanently. Slave 1 already got me a gold on Ison Corridor Ambush. Unfortunately I've read that that is all it's good for. It's slow as crap.

BTW it will be in the hangar behind the B-wing and next to the Falcon. It's kind of hard to see at first. It's really big, but it's gray and blends into the back ground a little.

To get to The Triumph of the Empire, press up on the control stick when you have Strike at the Core selected.

Use Slave 1 to get gold the Revenge on Kothlis level (the level where the crashed star destroyer is). It is kinda fun to use, I already had gold on the level. But its fun to knock out everything in sight.

Slave 1 has HORRIBLE shields, and it's slow as all hell.
Like 2 hits and you're gone. This is totally unrealistic. If you're the best bounty hunter in town, are you gonna have a slow ship that's easy to blow up?

I guess they didn't want to make a really cool ship that just made all the levels super easy though.
Ah well.

Courtesy of Gamefaqs, here are the remainder of the codes:

LIONHEAD - Black and white presentation of Rogue Leader.
BLAHBLAH - Unlocks the audio commentary.
COMPOSER - Unlocks the Music Hall in Special Features.
EXHIBIT! - Unlocks the Concept Art Gallery in Special Features.
?INSIDER - Unlocks Documentary in Special Features.
THATSME! - Unlocks Credits in Special Features.

JPVI?IJC, then RSBFNRL - Infinite Lives. Must be entered every time you turn your system on.
AYZB!RCL, then WRKFORIT - All Tech Upgrades.
!??QWTTJ, then CLASSIC - All Standard Missions.
PYST?OOO, then DUCKSHOT - Opens Death Star Escape mission.
TVLYBBXL, then NOWAR!!! - Opens Asteroid Field mission
CDYXF!?Q, then ASEPONE! - Naboo Starfighter.
ZT?!RGBA, then DISPSBLE - TIE Fighter.
MVPQIU?A, then OH!BUDDY - Millenium Falcon.

Think we'll be seeing Tie Bomber and Jedi Starfighter threads here?

I need the codes to open the Revenge on Yavin Mission and the Endurance Mission. I assume they exist since all the other codes for the "secret missions" have become available. However, I have never seen them posted anywhere so I assume they are not "out" yet. I got everything else in the game (great game) by myself (all ships) and everything open thru the first Darth Vader level. I have obtained a number of golds, but I just don't have the patience to finish getting the golds on a number of the other levels just to open Revenge on Yavin. I really don't care about Endurance actually. Revenge on Yavin should be fun though. Can anybody help?