Connecting … Solo Travel Network, http://www.cstn.org, can connect travelers with possible partners.
CouchSurfing, http://www.couchsurfing.org, connects travelers with hosts who lend their couches or beds. Hosts list profiles, dates available and the condition of their home. Travelers also have online profiles with their backgrounds, interests, hobbies and professions. Both hosts and travelers undergo a verification process.
Nonprofit Earthwatch, http://www.earthwatch.org, will match you with a roommate on its volunteer scientific research expeditions. The majority of its paying volunteers are single or traveling without a spouse.
GlobalFreeloaders.com, http://www.globalfreeloaders.com, helps you save money and make new friends while seeing the world.
At TravelersMeet, http://www.travelersmeet.com, and Lonely Planet's Thorn Tree, http://www.lonelyplanet.com/thorntree, you can post your destination and what type of traveler you are and search other posts to find a suitable travel partner.
SinglesCruise.com offers onboard programs as well as a free roommate matching service for those who want to save money by taking advantage of the double occupancy cabin rate.