I came across this method recently while trying to register for a training course off SAP education website. Apparently you could easily obtain an OSS ID through their website, granting you have access to the SAP environment at the company you are at.
Click HERE to access the registration page.
Upon entering this site, you will be asked to provide a few information. You will need a valid email address from the company you work for and the installation number.
The installation number could be found from SAP GUI. Inside SAP, click on system and status.
Once you complete this registration you will be given a temporary password. Write down the password as you will need it to complete the registration later on.
The system will send you an email to activate the account and registration. At which point you will need the temporary password you've obtained earlier. After you finish this registration process, you will be given an ID starting with the "S". You will be able to use this to log into http://service.sap.com and OSS Notes.