The jQuery BlockUI Plugin lets you simulate synchronous behavior when using AJAX, without locking the browser. When activated, it will prevent user activity with the page (or part of the page) until it is deactivated.
BlockUI adds elements to the DOM to give it both the appearance and behavior of blocking user interaction.
An alert alternative for jQuery that looks good. Apprise is a very simple, fast, attractive, and unobtrusive way to communicate with your users. Also, this gives you complete control over style, content, position, and functionality.
noty is a jQuery plugin that makes it easy to create alert, success, error and confirmation messages as an alternative the standard alert dialog. The notifications can be positioned at the top, topCenter (like GMail), bottom, centre, top left or top right. There are lots of other options in the API to customise the text, animation, speed, buttons and much more.