This is one of the most annoying features with Google Reader, the lack of search feature. But with time it was always bound to end up as a feature. Google Reader Official Blog announced yesterday that they have added the search feature to the feed reader.
You can see a new search box on the top of the page in the feed reader. This feature was previously available when you used a GreaseMonkey script called Google Reader Search but was limited only to Firefox users.
The other significant changes include being able to show and hide the sidebar with the click of a small arrow. So while your reading a feed you can get more screen real estate by toggling the sidebar. To toggle it you need to click on the small gray arrow that is provided.
And last but not the least the unread counts for the reader can count upto 1000, 900 more than the measly 100 they sported all this time, This will allow to easily see if you have 101 or 550 unread feeds.
Source: Official Google Reader Blog