I just use those green 'T' fence posts and they work fine for me. My beds are 4x25. I sometimes need to add a couple posts in the middle for a total of 6 per bed. It is great stuff!
Kirk

I use 1/2" rebar cut in 5' lengths. I have smaller diameter that I use in the middle of the beds as Kirk suggests. But ths smaller diameter bends! I like rebar because of the ribs that hold the net taut and I can move it as I move beds around. My beds are usually 3 or 4' by 25' and I end up with 6 posts per bed usually.

You'll really like the netting!
Wendy

We use 36" wide netting for most of our beds. Our beds are about 80' long. We use T-Posts, two at each end of the bed, and intermediate supports of 40" - 1" pipe (scrap from and old greenhouse frame) every 20' along the row, keeping hte netting tight side to side.
The trick is to place your T-Posts one square in from the edge of the netting, with the little nubs on the post facing away from the bed. Use a piece of 2x2 cut to the width of the netting, and cut a saw kerf across the end of the 2x2 to hold the edge of the netting. Weave the 2x2 through the end of the netting and stretch the netting over the T-Posts. Really lean back when you pull it over the T-Post. You want the netting really tight. You can adjust the height by locking the 2x2 in the nubs on the T-Post. By having the T-Posts in one square from the edge of the netting, you have elbow room for carrying buckets at the end of the row. The 2x2 helps keep the netting nice and tight and straight. Don't leave out the intermediate supports or you may have the middle of a long row lean over in a thunder storm.