Travel is considered to be a leader in the Web2.0 - its all about the community, sharing information, sharing knowledge, sharing experiences.
Travel blogs, travel forums, travel photo sharing (www.woophy.com, www.fotopages.com , and many more)
Travel has become cheaper, thus, travellers in the web2.0 phase look for cheaper options, "alternative" travel (example: www.skylow.com)
I hope it helps