I'm one of the co-founders of plaintextoffenders.com. We recently received a submission for which I'm not sure if there is a means of attack or not. The site in question is a hosting/VPS/etc. company.
Once someone clicks on Forgot Password, an email is sent to the user's email address. It specifies a password reset address (good) which is time-limited to 15 minutes (excellent) but also contains the user's temporary password for those 15 minutes (huh?).
While this is clearly not an indication that they are storing passwords in plain-text, it got me thinking whether sending the temporary password, along with the time-limited reset link, had any security implications.
Update: After reading your answers and going through the wording of the email carefully, I've found that the password supplied is not the temporary post-reset password, but the password that will be used permanently after the reset link has been clicked. This fits in with our mandate and the post will be published. Thank you all for your answers!