Twippera is a widget for opera which allows you to send and receive tweets through Opera. It was developed by a Japanese author, Higeorange, who has created widgets for tumblr and google suggest earlier. Although it satisfies a few of the basic needs, still a lot of functions are to be added to become a good twitter client. It starts with a memory usage of 30 Mb and later sets to 7 Mb.
Main Features:
-post messages to Twitter
-display friends timeline
-autorefresh option
-bit.ly and ff.im url handlings
-support for several languages.
You can download and try twippera from this page.