I’m on Chrome so some extensions may be Chrome only.
- Missing e (goes without saying)
- Tumblr Savior (goes without saying)
- Tumblr Hate - allows you to “hate” a post, which removes it from your dash, and also turn off notifications for a specific post (handy if you ever had a post go viral).
- Tumblr Hide Followers - if you’re like me and your follower count makes you anxious, hide it so you don’t ever have to think about whether anyone’s unfollowed you. (You might have to manually edit the script to keep up with Tumblr’s dashboard changes.)
- tBundles - bundle tags you use together a lot so you can add them all at once to a post.
- Stylish - not Tumblr specific but here are some Tumblr-related userstyles: Tumblr Multi-line tags, Tumblr - Missing E Warning Remover, Dashboard +Follow Remover
- Social Fixer - if you use Facebook and you don’t have this, I don’t understand how you use Facebook.
- Hover Zoom - Zooms a thumbnail image on mouseover on pretty much any site (you can disable it on any site too). On Tumblr this means you rarely have to click to enlarge an image.
- Flickr Photo Page Enhancer - does a bunch of stuff but for me the most useful is that it adds direct links to different sizes of a Flickr photo.
- Shut Up - disables comments on pretty much all sites — you can re-enable them by site though.
- Linkify Plus - automatically converts text URLs to clickable links.
- YouTube Options for Google Chrome - gives you control over YouTube — disable comments, automatically expand description, disable autoplay, set minimum size/HD level, disable annotations, etc.
All of these make my online life a zillion times easier! I hope they’ll do the same for you. This isn’t all the scripts/extensions I use, but they are the ones I figured would be most useful to the most people.