Clubhouse - Unlocked after completing Mission 5.
Grotto - Unlocked after inviting the agent to the special party in Mission 4.
Pool - Unlocked after completing Mission 1.

There are a ton of things to unlock in Playboy: The Mansion, based on your various actions. This is the complete list of what to get and how to get it in Mission Mode. The requirements are different for Freeform Mode, but all items are still attainable no matter which mode you are playing.

Publish Karmyn Chase on the cover in mission 5.

Sign Carmen Electra in mission 8.

If you take a picture of a girl while she is winking (so that the picture has one eye closed), it will boost your photoshoot.

Variety is the key to a great photoshoot. Get pics both on and off the bet, couch, or prop. Get some clothed and some topless. Get objects in as many pictures as possible. Get as many winks and raised eyebrows as possible. Also, fit them in the picture both close and far off.

Successfully complete mission 9.
Successfully complete mission 3.
Complete the fund raiser for Operation Validation in mission 5.
Successfully complete mission 5.
Invite the agent to the special party in mission 4.

To increase the Charm of people, have them follow you to a mirror and tell them to "Use". Repeat this several times.

Get your journalist to follow you. Take them up to a bookshelf and tell them to "Use". Repeat this many times. Eventually you will have increase their Intelligence. This also works with everyone in the game.

Just like how you can raise your photographers and writers intellect by making them follow you and telling them to use bookshelves, you can also do for Hef. His intelligence will also rise, but it sometimes will not work for the different bookshelves.

Have your Playmate follow you to a piece of sports equipment. Tell them to "Use". Repeat this several times. Eventually they will have a high Physique. This also works on everyone in the game.

Do an intimate action with a woman in mission 3.

Have a Sexy Grotto Party for the Playmates in mission 7.

Publish an issue in mission 2.
Publish the Playboy Philosophy in mission 4.
Finding Ken Willard in mission 5.
Successfully complete mission 4.

Have the special parties for your staff, Playmates, and girlfriends in mission 7.

Get a high romantic relationship level between any woman and Markus Jacobski in mission 6.

Successfully complete mission 1.

When you have a playmate do a centerfold. After you publish them, they can do an essay, cover shoot, or an interview. It is good to be their friend before publishing your magazine.

Successfully complete mission 8.
Successfully complete mission 6.
Successfully complete mission 11.
Successfully complete mission 10.
Have the two fighting staff members to reconcile in mission 4.
Successfully complete Mission 2.
Get a high romantic relationship level between Builder Paris and Karmyn Chase in mission 6.
Get Ciro Burrow and Wendy Bigmoney together in mission 8.
Get two girlfriends in mission 3.
Publish Karmyn Chase on the cover in mission 5.

Brass Bed - Upper floor only. Unlocked after completing Mission 9.
Bunny Back - Main or upper floor. Unlocked after completing Mission 3.
Butt-r-fly - Main floor only. Unlocked after holding the fundraiser for Operation
Validation during Mission 5.
Leg-O-Lamp - Main or upper floor. Unlocked after doing an intimate action with a girl during Mission 3.
Massage Table - Upper floor only. Unlocked after publishing an issue during Mission 2.
Michelangelo - Main floor only. Unlocked after publishing the Playboy Philosophy during Mission 4.
Obsession - Upper floor only. Unlocked after finding Ken Willard during Mission 5.
Olivia-s Hef - Main floor only. Unlocked after completing Mission 4.
Regency Chair - Main or upper floor. Unlocked after completing Mission 8.
Regency End Table - Main or upper floor. Unlocked after completing Mission 6.
Regency Rug - Main floor only. Unlocked after completing Mission 11.
Regency Sofa - Main or upper floor. Unlocked after completing Mission 10.
Trampoline - Pool only. Unlocked after getting two girlfriends during Mission 3.
Ultra Extreme Dance - Clubhouse only. Unlocked after publishing Karmyn Chase on the cover during Mission 5.
Artsy Bunny Shirt - Unlocked after cover shooting Karmyn Chase during Mission 5.
Barely There Plus - Unlocked after signing Carmen Electra to a contract during Mission 8.
Leopard Flares - Unlocked after holding the sexy Grotto party for your Playmates during Mission 7.
Plaid Skirt - Unlocked after holding the special parties for your staff, Playmates, and girlfriends during Mission 7.
Playboy Mini - Unlocked after getting a high romantic relationship between Markus Jacobski and any female during Mission 6.
Retro Zip-Front - Unlocked after forcing the two enemy staff members to make up during Mission 4.
Shoulder Wrap - Unlocked after getting a high romantic relationship between Karmyn Chase and Builder Paris during Mission 6.
Stars -n- Stripes - Unlocked after inducing love between Wendy Bigmoney and Ciro Burrow during Mission 8.
White Peek-a-Boo - Unlocked after getting Penny Starks or Sandra Bellore as your girlfriend during Mission 8.

Roster Character Editor - Allows you to edit the name and appearance of all fictional staff members and celebrities. Note that ratings, specialties, and occupations cannot be edited. You also cannot edit anything about storyline people in Mission Mode, such as Scotty Powers or Ki Kji. Unlocked after completing Mission 2.