Edinburgh dungeon is good fun, ghost tours and history tours are interesting, literary pub crawl is likewise pretty good (it's a pub crawl though, which I consider cheating). Then you've got the view from Arthur's Seat, the Zoo, the National museum (free), various other museums and galleries, various historical sites and monuments worth checking out too. Distillery and brewery tours, observatory, botanical gardens, numerous theatres and cinema's, the Scottish parliament, a metric **** ton of tourist traps all down the Royal Mile, Mary King's close, the catacombs, the royal yacht and quayside and ****loads of other stuff.
http://www.google.co.uk/search?q=edinburgh+tourist+attractions&ie=utf-8&oe=utf-8&**=t&rls=org.mozilla:en-GB

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If you don't mind travelling, you have Glasgow reachable by train (60 minutes or so), likewise Stirling. Blair Drummond safari park and the national seabird centre (Berwick) are similarly accessible by train (and Berwick itself is worth a visit). If you want to sample the Highlands it takes around 2-3 hours via train to get to Pitlochry, though how good that is really depends on the time of year. Linlithgow has a castle and loch, though there's not much else to do there it's only 20 minutes out on the train (and on the way to Stirling or Glasgow). Finally, if you're into hiking or cycling you have a number of good trails to pursue, including the Union canal route between Edinburgh and Glasgow.