Down here, there are lots of welding places which sell pipe which has been welded together specifically for fence corners.
These are in H shape or maybe three vertical posts with two cross braces welded in.
You drill the post holes, drop in the welded corner, cement it in...and it's there for at least 60 years. The welds on the cross braces make the entire fence end rigid...doesn't pull out of the ground easy at all, easy to connect the wire of your choice also.
You can have variations on the theme...fence corners that are L shaped, or T shaped, etc.... hope this is clear
These people will weld up anything needed in this area.
http://killeen.craigslist.org/grq/4361060059.html
I see lots of people with various levels of experience with wood posts. I've been on my place for 30 plus years..started with the green treated posts...lots rotted out...moved to the more yellow treated posts...rotted out as well...I understand the comments regarding not sitting the post in a depression, piling dirt up around the post, etc....did that, rotted anyway...neighbors told me this would happen before I tried it...should have listened.
I've used creosote posts left by power company...work kinda, but I can show you several I stockpiled and are all rotted out when I went back to them to use them some years later. The best wood post here is the Ashe Juniper which is native...people call it cedar here...the heart wood is extremely hard and bright red...heart wood is very rot resistant, think 50 plus years....very difficult to find posts which are sufficiently large where the red heart wood is 5 inches on the small end and with long, straight posts. When you do, you are quickly into the price range of drill stem pipe which is uniformly straight and rot free.