WebPredict allows user to rate some Web pages, and based on those ratings predicts the quality of other Web pages. We made a beta-release of this add-on recently, and this beta-release prompted me to write this review.
The add-on is here https://addons.mozilla.org/en-US/firefox/addon/14273, and the server site (if/when one needs it) is http://www.webpredict.net/wp.
One can either choose to use this add-on anonymously or to create a WebPredict account. Both choices can be made via the right-click mouse menu, and if one wants to rate the page one is reading, this can also be done via the right-click menu.
There are various ways to ask for prediction of the quality of the page. One can hover over a link and press 'p' to obtain the prediction for the page behind the link. One can use Tools command in the browser menu to see more commands associated with this add-on, including "Predict Current Page" (this command has Ctrl+Alt+Shift+P shortcut; another shortcut I often find useful is Ctrl+Alt+Shift+C to clear WebPredict messages).
I usually set "Auto Predict Current Page" via add-on Options, and then the add-on tells me automatically what it thinks about the current page, but many people might find this too intrusive, so this is not on by default. One can also use add-on Options to set "Predict by Mouse Hovering", then simply hovering over the link would trigger the prediction.
Pressing '.' while hovering over the link allows to display prediction for multiple links around the current one (Ctrl+Alt+Shift+L would display predictions for multiple links around the cursor). Predicting links might not work if a Web site scrambles its page (unfortunately, Google does scramble its search results, and we don't handle this yet).
An anonymous user gets default settings, which are reasonably similar to the setting I am using for myself. If one creates an account one can go to the server page and tune one's rating categories and prediction settings in all kinds of ways (we do try to open our engine to the users, although for now we just provide a lot of knobs to control and tune it). If one creates an account, one can share ratings between different computers. If one first works anonymously and then creates an account, the ratings made anonymously are inherited.
I currently have about 25 ratings, and predictions usually correlate well with my own estimates. (When they don't, basically, when I feel the model does not rate a page correctly, is when I add a rating for the page in question.)
This is still experimental. We are trying to see whether it is useful in its current form, and what should be done to make it more useful/popular.
TooManyTabs allows user who has too many tabs to save tabs, so that they don't eat memory and don't slow down the browser.
The add-on is here: https://addons.mozilla.org/en-US/firefox/addon/9429, and this is its home page: http://www.visibotech.com/toomanytabs.
It allows you to manage multiple rows of saved tabs. It saves both the URL and your scrolling state. You can backup your tabs into a file in JSON format and restore from such a file. So you have your URLs in a plain text form, and you can even exchange your saved tabs between computers.
Note that memory management in Firefox is still quite imperfect, and the memory often is not released as you close the windows. This means that if you have too many tabs, and this slows your browser down, and you save some of them using TooManyTabs add-on to free some memory and to make it faster, you might still need to restart the browser in order to see the improvement.
I should say that this add-on makes my life much better. I can keep the tabs I like without losing them, and still have a browser which works fast. Nevertheless, I am still looking for better tools to manage large collections of URLs.