This thread is old but I'm just gonna throw up some of my favorite RAGs games, since they are what got me into this in the first place. Not mentioning Trap Quest because it was already mentioned. Of the four I've listed here, 'cursed' is the closest to a real sissy game (since you are a man turned into a girl instead of just.. a girl). But you play a female in all of them and, well, they're great.
cursed by Anonymousman (that's the creator's handle)
http://www.tfgamessite.com/index.php?module=viewgame&id=1
You go out to the bar with some friends, get cursed by a witch( or something? it's been over a year since i've played), turned into a female and have to restart your life with your new circumstance. It's all text but it's one of the best game systems ever put into one of these games imo. You choose a job, manage the money you make (buy wardrobe upgrades, stuff for your house, food, etc), balance your time, try to stay healthy and fit and IIRC have to balance an insatiable libido.
bodywerks by Darstan
http://www.hypnopics-collective.net/smf_forum/index.php?topic=14623.0
Unfortunately you need to register with this forum to download this one, but it's a great one! Worth several hours of playtime. You wake up in a hospital surrounded by over-sexed and often transformed slaves and work to unravel a mystery of how an evil corporation is kidnapping and brainwashing women to be sex slaves. But only if you don't get brainwashed yourself ;). This is less of a sim and more of a story-driven game. There are hidden items scattered around but there's a lot of trial-and-error to find what helps your character and what leads to a "bad end". Also it contains a couple of different 'real endings' depending on how you play your character.
overseer by dollmistress
http://www.tfgamessite.com/index.php?module=viewgame&id=267
I can't much remember the plot on this one, and it has quite a few faults (difficulty curve is like a cliff, first half hour or so of gameplay is nerve-wrackingly obtuse and difficult but then it becomes too easy. Also loading times are off the charts for this style of game). However, the gameplay is fun once you get passed the learning curve and the amount of content is off-the-charts. You start off with a base of operations and you have to go out into the world and create your own harem of mind-controlled slaves to help renovate and rebuild the base. Then you use those resources to complete story-driven quests and it culminates in a final showdown or two. Features multiple real-endings and quite a few 'bad-ends', as above.
The lilith device by CaptainSkel
http://www.tfgamessite.com/index.php?module=viewgame&id=293
This game is very similar to overseer, yet it doesn't contain the same obscene load times. But the content is off the charts, again. You find a device in the woods that opens into a secret facility (in another dimension or someth). And you travel around town trying to 'convert' other girls to join your harem/cult/facility. Develop your character, manage a budget, manage and develop a base of operations, purchase goods and use all these tools to complete storyline missions.