I have become a diehard Firefox user. IE does not hold the same thrill for me that it used to. And I also recently found out that my husband has been using it as well! He used to be very much content with IE and saw no reason to make the switch. One of my my favorite things about FF is being able to utilize add-ons. I figured it might be nice for all of you out there to see what I use all the time in case you are interested!
Download Statusbar: A great tool that shows the current downloads in the statusbar.
Down Them All!: A separate downloading window that allows for a queue to download. It's nice when there is a lot of media you want to download from one site, but you do not want to stay on the page all day to do it. All downloads can be paused, which is even better.
Drag Drop Upload: I use this add-on every day. When there is an uploading form, say on a social media site, if you have the folder open on the computer, the file you want to upload can be dragged from the folder to the upload field without needing to search for it. Much, much quicker than searching each time you need to upload. Just make sure you hit the upload field just right, or the page may load your file instead.
FireFTP: A free FTP program that works great. C uses this everyday on the site he works at.
Foxmarks Bookmark Synchronizer: I bookmark a lot of websites. This add-on allows you to create a username and save the bookmarks. You can download them onto another computer. When I was having computer problems last summer, this was a lifesaver!
Read it Later: I have mentioned this one before. This allows a right click on a link or page which is saved in the favorites/bookmarks that allows you to look at a page without permanently saving it into your bookmarks. For reading later, as the name implies.
Sxipper: A password saver, plus fills out forms. Can be a nuisance sometimes, but most of the time is helpful.
Retail Me Not: I don't use this one that often, but it is nice, at times. Retail Me Not is a site that provides thousands of coupon codes for online shopping. The add-on pops up with code information when certain websites are accessed.
Save Image in Folder: I actually have not used this one yet. I have had it installed for months and always forget to utilize it. This add-on allows the user to save an image in a specified folder quickly. I think that it works well, and got great reviews.
EDIT: I tried this one after I wrote this post, and it is awesome!! Very much a time saver for me. I often save the same photo in 2 different folders, so this was just great for me.
Better G-Reader: I have just started using this one. It's decent, but not perfect. This add-on is for Google Reader. When a user clicks on the title of a post in the reader, it loads the webpage of that link right in GR. You can even comment right in GR. Sometimes it messes up, though, and does not go to the correct page after clicking on a link. I like it so far, though.
That's my list of my favorite add-ons for Firefox. Hopefully it was helpful and points you to more add-ons that you can use in your webbrowsing.