It’s a long afternoon at work – or a late evening alone – and you’re looking for an easy way to browse through some links you might find interesting. Where do you go? What if you want to limit your browsing to just links which were tweeted? Where do you go then?

Well, if you’re also a fan of Stumbleupon, the answer should be Tumbl.in. Basically, Tumbl.in is Stumbleupon for Twitter links, limited to your lists and favourite topics. It’s easy to use and quite a powerful way to read your Twitter links.

Once you start to use Tumbl.in, you’ll see the similarities with Stumbleupon. It’s set up as a top-loading menu which brings in each link as an iFrame. When you view each link, you can choose to retweet it, rate it, save it for later or just click the Tumbl.in icon for another link. If you prefer, you can browse links from a given sub-section of your available Twitter links.

When you set up Tumbl.in, you do so by authorising access to your Twitter account. Once this is done, you can choose a selection of your favourite topics, favourite Twitter lists and other options to ensure you get the best possible selection of links to read later. You can always change things later in preferences, so just pick whatever looks good and go with it.

If you have chosen to include staff picks, you also get occasional links which are popular on Tumbl.in and have been chosen to be featured by the staff at Tumbl.in.

It can take a little while to gather your Twitter links, so when you initially start Tumbl.in you might find occasionally give you a message telling you it’s still looking for links. When the link is shown, you see the associated Tweet by looking in the top left. This means you know exactly who tweeted the link, why it appears in your Tumbl.in selection and you can pass on the karma by retweeting the update if you like.

As you view the links, button options let you rate it in Tumbl.in, retweet it, keep it for later or just move on to the next link by Tumbl.in again. It’s really easy to do, so it’s perfectly compatible with those late evenings when you’re not quite tired enough to go to bed.

Obviously, the biggest threats to Tumbl.in is Twitter and Stumbleupon. If either of those two giants had a go at something like this, most people would use that service rather than this one. That’s not to say they would be better, merely that people forget about useful tools easily.

Another form of competition for Tumbl.in is any other way of viewing your Twitter links in a comprehensible manner. For instance, the Twitter Times. However, I think Tumbl.in is different enough to hold its own market.

Check out some more great articles on Twitter tools:

• 3 Great Twitter Tools To Simplify Your Twitter Reading
• 8 Top Twitter Track Tools to Organize the People You Follow
• The 6 Best Tools To Schedule Twitter Updates
• Twitter Clients ““ Web Apps or Desktops Apps? Which is Better?
• 6 Twitter Web Apps to Ask Questions From a Twitter Crowd
• 5 Twitter Translation Tools That Help With Tweets In Other Languages

If you’ve become a fan of Tumbl.in, let us know why in the comments!