SendPSN Tools and now PlayStation 4 developer Dr. Luckeyy released a Gamer Choice Sony PSN ID Availability Tool that allows you to check whether a PSN ID is available or in use already on Sony's PlayStation Network when Creating an Account at your leisure.
Download: PSN ID Checker.rar (20.3 MB)
For those who are new to PlayStation Network and planning to register a PSN ID here are some tips from Sony that may be of use as well, to quote:
How do I choose my Online ID?
Please bear in mind the following when choosing your Online ID:
Thanks to @HydrogenNGU for the news tip on Twitter!
- You cannot change your Online ID once it has been created, so choose carefully.
- Your Online ID must be three to 16 characters and can consist of letters, numbers, hyphens (-) and underscores (_).
- We recommend that you do not use an Online ID that might personally identify you to other users.
- We do not allow vulgar or offensive Online IDs that violate the Community Code of Conduct. If you have an offensive or vulgar Online ID you may find that your account or PlayStation system is banned in line with the Community Code of Conduct.
- You may find that your first few choices of Online ID have been chosen by another user. Be patient and make as many attempts as you need to until you are happy with your chosen Online ID - don’t forget you can’t change it once you’ve decided.