For a concise review of some of the main evidence of Tibet's long history as an independent nation as well as informed updates on the continuing struggle of the Tibetan rangzen movement see Jamyang Norbu's blog "Shadow Tibet"
Norbu's blog takes a rather dim view of the Dalai Lama's "middle way" approach of seeking "true autonomy" with the PRC. The entry detailing the Lhasa uprising of 1959 was also a good read. The blog is not all politics though. The entry on the Losar cookie the khapsay was also something I had never come across before.