What these opportunities typically turn up to be is a pyramid scheme. You pay a fee to signup. You then receive a flyer saying how great stuffing envelopes is and list of names and addresses to mail said flyer. IF those people pay that signup fee so they can mail that flyer too, you get paid a small referral fee. ONLY if they take the bait do you get paid.
If you love to travel and find yourself randomly searching for airfare sales or browsing Lonely Planet, why not carve out a niche for yourself as a private travel agent? My friend, Mark Jackson did just that, making extra money online with his travel consulting side business. Start with word of mouth recommendations from friends who know they can count on you for the cheapest flights, and then move on and create a Facebook or LinkedIn group to invite people who want to stay on top of the latest deals. Eventually you could spin this into a full-time consultancy teaching people how to make their dream trip a reality.