I’ve always found it difficult to follow Twitter conversation threads.
So I’ve written a Greasemonkey script to automatically retrieve and display nested replies. The script recursively follows the “in reply to [user]” and gets the entire conversation thread. Install it here.

Note that Twitter links replies to the last update made by the original poster, so some threads may appear broken.
This is a simple PHP script to interact with the Twitter API and update the user’s status. Unlike most other samples, it does not use cURL or any other dependency.
$msg = 'Your message here';
$out="POST http://twitter.com/statuses/update.json HTTP/1.1\r\n"
."Host: twitter.com\r\n"
."Authorization: Basic ".base64_encode ('username:password')."\r\n"
."Content-type: application/x-www-form-urlencoded\r\n"
."Content-length: ".strlen ("status=$msg")."\r\n"
."Connection: Close\r\n\r\n"
."status=$msg";
$fp = fsockopen ('twitter.com', 80);
fwrite ($fp, $out);
fclose ($fp);
Note that this script does not store or process the response.
The Orkut scrap feature is very similar to Twitter, expect that it sucks. It is overrun by spammers, you need a captcha to post links, and conversations are impossible to track.
When Orkut user A wants to “scrap” Orkut user B, A scraps B’s scrapbook, and B responds in A’s scrapbook. Just like an email. Wouldn’t it have been better if A wrote in A’s scrapbook and B in B’s scrapbook ?
That is a little like what Twitter is.
To be fair, the scrap feature was never intended to be used this way. This is what Orkut says the scrapbook is for.
The scrapbook feature is another way for you to add tidbits of information to your profile.
It was intended to be a micro-blog like feature, not a conversation enabler.