At the 'Main' menu press ALL four of the shoulder buttons together to bring up the 'Cheat' menu and then enter the following passwords to unlock the corresponding feature of the game.

Unlock ALL 2-Player games, ALL Locked Objects and ALL Locked Skins:
Enter the password 'MIDAS'.

Unlocks the Play The Sims Mode without going through the Get a Life Dream House:
Enter the password 'SIMS'.

Unlock Party Motel 2-Player Game:
Enter the password 'PARTY M'.

ALL Objects Cost 0 Simoleans:
Enter the password 'FREEALL'.

Unlock First Person View:
Enter the password 'FISH EYE'(during the game press O to change walls and when the walls have gone press O again to change to a 1st person view).

The following are ALL unlocked by getting through the indicated stage in a certain amount of days.

Unlock Beejaphone Electric Guitar:
Get through Stage One: 'Money From Mom' in 24 hours or less.

Unlock Highbrau Coat of Arms:
Get through Stage Two: 'Reality Bites' in 4 days or less.

Unlock Head in Curio Jar:
Get through Stage Three: 'Party Animals' in 8 days or less.

Unlock Wurl 'N' Hurl Retro Jukebox:
Get through Stage Four: 'Hot to Trot' in 8 days or less.

Unlock Bearskin Rug:
Get through Stage Five: 'Who Loves Ya, Baby?' in 8 days or less.

Unlock Rhino Trophy.
Get through Stage Six: 'The Last Simoleon' in 8 days or less.

If you purchase the telescope and use it for too long your Sim will be abducted and vanish but will reappear some hours later with different stats.