Google are offering us UK folk the option of now switching from @googlemail.com to @gmail.com after finally winning a battle that has been going on since around 2005.

Here is the link to directly change (you need to be logged in!)
https://mail.google.com/mail/googlemail/rebrand [dead]

BBC News – Googlemail to become Gmail in UK
Google Mail is becoming Gmail in the UK – Official Gmail Blog

Here’s a little known fact:
Even though we have had @googlemail.com addresses until now, “secretly” we’ve also had @gmail.com addresses, which were simply not shown. If you have the account firstname.lastname@googlemail.com and someone sent the mail to firstname.lastname@gmail.com you would still get it.

Didn’t know that? Why don’t you try sending a mail to yourself with the alternate address? That includes you @gmail.com users! Prefer @googlemail.com? Then use it! Simply set up a send mail as in settings > accounts, follow the on-screen instructions and you can choose which email address you want to send from. It really is that easy.