<p>Reading on another forum I've came across the world of CSS Frameworks. The one I've been specifically looking at is <a href="http://www.blueprintcss.org/" rel="nofollow noreferrer">BluePrint</a>. I was wondering if anyone else had come across CSS frameworks, suggest which is the best and if they are worth the effort?</p>

CSS 'frameworks' are completely missing the point.
CSS is not like JavaScript, where you can include a base library/framework and then call functions and objects from it to do higher-level work. All a CSS framework can give you is declarative rules: some default browser-rule-reset stuff, some class styles to be forced to author your page to, and layout rules using 'float' and 'clear'. You can write that in a few lines of CSS yourself rather than pulling in the bloat of a hundred framework rules.
The 'grid layout' stuff in particular goes back to the bad old days of mixing your presentation into your markup. 'div class="span-24"' is no better than a table, you'll have to go back in there and change the markup to affect the layout. And all the frameworks I've seen are based around fixed-pixel floated boxes, making it impossible to create a liquid layout accessible on a wide range of window sizes.
It's backwards authoring, of use only for someone too scared to write a CSS rule.