Do you want to host your wordpress plugin in wordpress plugin database? Start here.
The first step before you actually submit your plugin, is to have yourself registered at wordpress.org. Well, registration seems very easy. But, if you have a dot separated email id like mine, be ready to see the error:
There was a problem with your email; please check it.
I think, it treats the stuff after the first dot as the email provider domain and hence treats it as invalid email. If you have google email, then my technique will work for you. Google allows your email without the dots, also to be your email. e.g. if your email is email@example.com, google allows you to use it as firstname.lastname@example.org. So, provide dot free email while registering for wordpress.org account. You will get the password mailed to you in few minutes.
Next, you need to get the access to the wordpress.org subversion (SVN) repository where you can put your plugin. Fill this form to request the access to repository. Fill all the fields carefully, as the repository will bear exactly the same names.
Wait … Wait … Wait for the approval of your request. Usually it takes hours to get the approval. It took almost 8 hours to me. You will receive a mail with details of the SVN and few helpful links listed below:
Here's some handy links to help you get started.
Using Subversion with the WordPress Plugins Directory
FAQ about the WordPress Plugins Directory
WordPress Plugins Directory readme.txt standard