WidgetLogic
http://wordpress.org/extend/plugins/widget-logic/ Here are a few examples of widgetlogic you can use:
is_category(X) || (is_single() && in_category(X)) - if viewing Category X or a post within Category X.is_archive() - if viewing any...
As the pendulum shifts from content to data, the logic that once guided our thinking about search will change and our hesitation to limit what we show Google will fade. Basing your strategy around adding a Google+ widget to your site will be the...
Tip: Hashtag logic can be planned based on the post's category. If you're using those old tools, upgrade to the new code or chose a different widget. Mashable uses ShareThis with their responsive web design; depending upon screen width, the social...