Am I all alone in the Waste?

There's also Clover; a Slave in Paradise Falls. Evil karma required.
Butch; from the Vault. You need to do the quest "Trouble on the Homefront" first. Then found in the Muddy Rudder bar in Rivet City. Neutral karma.
Sargeant RL3; a mister Gutsy robot. You usually meet a trader outside the robot place near Tenpenny Tower, and you can buy the Sargeant from him. Neutral Karma.
Star Paladin Cross; A cyborg that's highly ranked in the Brotherhood of Steel. Found around the lab, where the robot is. Good karma.

There are eight followers. Two for good Karma, Two for Neutral Karma, Two for Evil Karma, and Two for any karma. Here are the ones you're missing:

Good:
Star Paladin Cross: Find her in The Lab in The Citadel. By default, she has a Super Sledge and a Laser Pistol. If your Karma shifts to evil while she's with you, she'll leave your team.

Neutral:
Butch: Found after Trouble on the Home Front. I've heard that there are some outcomes of the game after which he won't be found, but most outcomes you'll afterwards find him in the Muddy Rudder in Rivet City. He fights with a Switchblade called Butch's Toothpick and a 10mm pistol.
Sergeant RL3: Found around the Robco factory, following a scavenger. He'll sell you the Sergeant if you have Neutral karma and 1000 caps to pay. Uses a built-in flamer and plasma shot.

Evil:
Clover: Found in Paradise Falls. With evil karma, you can buy her off of Eulogy Jones for 1000 caps (Less with a high enough barter). Uses a Chinese Officer Sword and a Sawn-Off Shotgun.
Jericho: Found in Megaton. Will only join after you pay him 1000 caps. Uses a Combat Knife and a Chinese Assault Rifle.

Any:
Dogmeat: Find him in the scrapyard fighting off some raiders. Will join you upon talking to him. Generally considered the weakest follower and most likely to die randomly, but fills an extra slot that normally only he can fill, allowing you to have more followers, and also part of an exploit to get as many of these followers as possible.

There are also a handful of temporary followers:

Sticky: Found in Little Lamplight. Likes to use big guns. If you don't pass a speech check on him he won't shut up in your travels. Will leave your party if you go to Big Town.

Red: Found in the Germantown Police HQ during Big Trouble in Big Town. Will leave upon returning to Big Town.

Shorty: Found in the basement of the Germantown Police HQ during Big Trouble in Big Town. Will leave upon returning to Big Town.

Sydney: Found in the National Archives during Stealing Independance. Part of an exploit for infinite caps. Will leave upon completion of Stealing Independence.

Bumble: Gotten in Little Lamplight with an unmarked quest and exploit. Useless. Will not fight, runs away from battle.

Cherry: Found in Duskov's place. Can be gotten during You've Gotta Shoot 'Em in the Head! Isn't very useful in combat, and will return to Duskov's place if not taken it Rivet City within 5 in-game days.

Overkill, yes, but I hope you find this useful.