Online Dating

You definatly need something that can store data, perferably a database. I would use PHP. You will need a server which has PHP installed also. For display, HTML should be fine.

you need a lot of people who wan’t to date but can’t get a date themselves

Database driven technology such as PHP, or ASP, a backend database such as SQL, or MySQL, a suite to build them in such as Dreamweaver or Visual Studio(but VS is not so good when it comes to laying things out) and a graphics package wouldnt go astray such as Photoshop, it depends what sort of features you are trying to achieve, also a web server that supports the chosen technology would be useful, such as IIS/Windows for ASP/SQL or Linux for MySQL/PHP, if people will exchange personal information SSL would be recommended, but as its free prob not required as theres no transactional data.