Basically you need a mashup, which aggregates content from many sources and lets you filter it. You can do it using Yahoo Pipes.
First, convert all your sources to XML or RSS feeds. Pinboard provides an RSS feed: https://feeds.pinboard.in/rss/u:patku/ but for Twitter you have to use RSS 4 Twitter. For other sources you can use the fantastic YQL.
Then, create a new pipe, combine all your sources into a single feed, add a user input for a query and filter this feed.
Finally, output the filtered feed as a widget. Done!