If you like Flickr's explore section but want something with a little more personalization, you should check out Photoree. It's a photo browser that lets you rate a photo up or down like what StumbleUpon does for Web sites. As you continue to rate photos, the engine will tune itself to your tastes--hopefully spewing out more shots you'd find pleasing.
The engine says it needs 100 ratings from you before it can start figuring out what you like and what you don't. In that time you'll probably see a huge chunk of landscape shots and some scantily clad women--at least I did. If you're worried about something offensive popping up on screen there's a no nudity filter that does its best to weed out the NSFW material, however, on or off, you're unable to see what photo is coming next.
There are five different filters in all, but the personalized one is the site's main draw. The others like "most debated" and "most popular" serve up only truly gorgeous shots that have been vetted by other users. Going through the recommendation process yields a potentially better mix of shots.
My problem with this system is that all the photos I saw, even during the first 100 ratings, were drop dead gorgeous. You're going to have to be quite picky with how you rate them for it to work its magic. More than anything I noticed the frequency of shots similar to what I had favorited going up after breaking the magical 100 mark. The tool would be far more interesting if it started you off in a general pool of users shots (even ugly ones) instead of taking you straight to the good stuff that's already been given the thumbs up from both the Flickr and Photoree community.
The tool does have some really fun layers of interactivity to play with, like built-in bookmarking for the shots you like. You can simply click on any of these to be taken to the Flickr page where it's hosted. It'll also give you some neat statistics like which other Photoree users share your tastes and which Flickr photographers you like the best. After 105 ratings I had achieved about 50 percent compatibility with a good number of users, and after tipping 280 it bumped up close to 60. You can befriend these folks to get access to their up-rated photos, or see them openly if they've set their feed to be public.
Another service that's somewhat similar is inSuggest's image suggestion tool (coverage). This lets you drag three images you like from a pool of thumbnails and it will link you to a handful of shots it thinks are similar. The same company makes a tool that analyzes your bookmarks and taste in Web sites as well.