Here is how to search the [Egyptian Blogosphere|http://egybloggers.com/]. I guess this would be very useful.
Go to [feedster advanced search|http://feedster.net/advanced.php], type your keyword and then add [this OPML file|http://www.manalaa.net/aggregator2/opml] in the space titled "Limit to feeds in this OPML URL".
UPDATE: the above photos is a bit old please use this url http://www.manalaa.net/aggregator2/opml
One more thing, feedster is a little bit strange. You will have to search every time from the Advanced search page.
Here are several examples: