Peter Westwood

WordPress Version Check provides you with an easy way of checking that you are running the most up-to-date WordPress version. The plugin checks an XML-RPC webservice every 15 minutes for update information and displays a message in the admin pages.
Note this plugin is no longer useful or supported so don’t bother installing it
See this blog post for more info: http://blog.ftwr.co.uk/archives/2009/05/26/retiring-wordpress-version-check/

WordPress Version Check

WordPress Version Check provides you with an easy way of checking that you are

Jon Cave

If you don’t check your admin panel on your WordPress install very often (maybe because you prefer to use remote publishing) or you want to make sure 
that your clients’ WordPress installations are updated, then this is the plugin for you. You don’t have to login to your admin panel regularly, 
suscribe to an RSS feed, or do anything apart from installing this plugin to be notified when an update to WordPress is released.
All you have to do is install Update Notifier and forget it until you receive an email telling you to update.
To change Update Notifier’s options, go to Update Notifier under the main Settings menu. From there you can add a secondary email address 
which will also receive update notifications and you can activate update notifications for themes and plugins.

Update Notifier

Sends email notifications if a new version of WordPress available. Notifications about updates for plugins and themes can also be sent.

WordPress Version Check vs Update Notifier