Extended travel does not negatively impact your job search for the vast majority of careers.

About 2 years ago I quit my job, got married and traveled around the world for 6 months. I had been consulting for almost 3 years and when I got back I spent another few months working on startup ideas.

Travel
Andy Anderson does good job of addressing the planning questions about the travel itself, but I have a few points to add:

• Pack the same for a month as for a week - if you travel for 6 months you will need to take seasons into consideration, bring lots of layers. However, for any given climate/season you should not bother with more than one to two weeks of clothes. You will need to do laundry - whether you get laundry service in SE Asia, use a washing machine in your hostel, or hand-wash clothes on the washing stones at a farm you'll get to see a very real part of the local life and you'll not break your back with 6 months of clothes.
• Plan not to plan - it takes about a month to plan a well-thought out week-long vacation. You need to pre-arrange transport, optimize your dates and times based on the hours of the sites you visit, and you don't want to waste time looking for hotels. When you travel for 6 months, you don't need to plan everything. Looking for accommodation, asking locals whether to fly or take a bus and even haggling about the price of a boat-ride is a great way to meet people and explore your new city. In our trip, we bought only transcontinental flights in advance and everything else was booked during our travel, e.g., we landed in Quito, Ecuador and had 40 days to get to Rio for our flight out.

Job-Search
Looking for work after a year-long leave is about crafting a story appropriate for the job you are seeking. Most managers either like to travel or understand that other people like to travel - no one has ever asked me for an explanation of my trip in an interview - just travel advice.

• Your trip makes you different - as a consultant I conducted a few interviews and looked over piles of resumes. It's really boring to interview your eighth under-grad economics major with a 3.7 GPA who did student council and intramural basketball. The fact that your profile is not identical to everyone else's actually helps you stick-out in your interview.
• Talk about your trip (but not too much) - potential employers are curious about gaps in your resume, but going on a backpacking trip is a great explanation. You should summarize your trip quickly in your interview - how long it was, where you went, and one exciting thing you learned/experienced - and then, only if you are asked for more detail should you continue discussing your trip

If I have more time, I will try to add to my answer...