I removed a couple recently using the dig-a-hole-next-to-it-and-pull method. Works just fine. I also used a section of a log as a "wheel." Kind of combined two techniques, I guess.
Back in 1969 I worked with a guy putting in chain linked fences and removed a lot of post in concrete. All you need is a come-a-long. Hook the come-a-long to the bottom of the post and hook the other end to the top of a another post and set the bottom on something sturdy and winch it out.