I�m pleased to see someone considering RTW travel. It�s certainly more sensible, economically, than many of the point-to-point fares.
You�ve mentioned �open-ended� travel. Apologies, but do you mean �open-jaw,� where you fly into one city and out of another? Or are you referring to simply �open� tickets, where you have the �city-pair� (from and to) on your ticket, but no date?
The first place I�d start is with the two major �alliance� groups: Oneworld and Star Alliance. Keep in mind, that you can accrue frequent flier miles on all the sectors through them.
In the first instance, have a look at:
http://www.oneworld.com/
Then, have a browse through:
http://www.staralliance.com/en/travellers/inde x.html
In most instances, the RTW ticket is valid for either six months or twelve months. You must always continue to travel in the same direction. Open Jaws are permitted, some countries have maximum stopovers (such as the USA). Open sectors are no problem and there is no fee for booking those flights at a later date. However, anything involving having to change the board point and/or off point does bear a fee.
May I please ask what general ideas you have for your journey? I may be able to offer some advice as to which group may benefit your plans.
I wish you well
Fr Bill