The one I love most is called "My Candy Love". It is available in various languages such as spanish, english, german, french, etc. It has episodes, and each episode builds onto your high school story. You have to register, but you can choose your name and appearance. There are also a wide range of boys you can build your relationship with, and at the end of each episode you'll get an illustration depending on the choices you made throughout the certain episodes. As the story goes on there will be more and more guys to choose from, you'll know more people, and will have a wider range of illustration choices. There are also special characters that are only available in certain episodes. There are also special episodes for Christmas, Halloween etc. You can replay each episode as much time as you want, but the special episodes cost action points. You don't have to pay for dollar or action point with real money if you don't want to, each day you log in, you get 15 dollars and 10 actions points. You have a wide variety of clothes you can wear, but obviously you'll have to pay for it with in game dollars. Also each time you make a moving(eg. going from the classroom to the hall) will cost you action points. It is a well worked out game and the art is really pretty too, I highly recommend it, if you like sim date/otome games. This game now also has a free phone app called the same.
There is one a little bit similar to this called "Star project". It is online as well, and requires registration, but is free unless you want to pay for extra energy or money in order to progress quicker in the story. The difference is, that unlike in My Candy Love, you are not a high schooler, instead you are a music agency that hires people, and you hire boys and build friend/relationships with them. In this you do not get episodes, but by doing different gigs and other activities you unlock different scenarios and illustrations. As you progress along the story you'll get more options depending on the skills and time you spend on each of your "stars". It is a really cool game, although it is still heavily under progress and being improved, so there are still aren't many characters, but on the website you can see characters that will be developed in the future.
There are also many online flash dating games by Pacthetis, that are usually called "....... Days" (eg. Kingdom Days, Number Days). They are short online stories. They are well done, and even though the art isn't perfectly done, it is pretty cool. You usually get 8 different ending with at least 4 different guys and have 30 days to seduce the guy of your choice. She has made various games, and with each game there's a really cool and different story. You can find more out more about her and her games on her deviantart, that is runned by the name "Pacthetis".
There are also really pretty and cool otome games for phones, you can download. Some of my favourites are Ninja Love, Destiny Ninja, Love Academy, but there are many others that are free to download. But be careful, even though the app is free to download, sometimes, they give the prologue, but after that, they do not let you continue on unless you purchase the full game, eg. My Forget Wedding, In your Arms Tonight, and pretty much all the otome games created by Voltage Inc. The art is really beautiful and the prologue is really interesting, but after that they'll ask you to pay money to continue on with your story.