Aside from the obvious stuff like dragons, giant spiders, etc. many people have commented on how the world reminds them either of Tolkien's work or the LOTR films.
A few examples:
http://img593.imageshack.us/img593/1589/skyrim01.jpg
http://static.zenimax.com/bethblog/upload/2011/02/vlcsnap-2011-02-24-11h23m58s200.jpg
http://www.godisageek.com/wp-content/gallery/elder-scrolls-v-skyrim/skyrim-screenshots-dragon-mountains.jpg
http://2.bp.blogspot.com/-9KPQdIXDthk/TVf6PZQ5U4I/AAAAAAAAAN4/bgneer-6Sdo/s1600/8.jpg
A lot of the concept artwork we've seen glimpses of in videos shows even stronger similarities, and there's areas we haven't seen yet like the glacial regions of the map, which immediately make me think of the http://img-fan.theonering.net/~rolozo/images/nasmith/new/TN-Fingolfin_Leads_the_Host_Across_the_Helcaraxe.jpg in Tolkien's work, or the rocky / volcanic tundra regions which make me think of the lands surrounding Mordor.
As a huge Tolkien fan, i'm loving the similarities. Anyone else agree?