i mostly use bamboo and nylon trellises, in some form. i love boo- it's strong, and holds up for several seasons and even when it's getting crochety i can find many uses for it. i've done trellises in an upside down U shape, an upside down V shape, and a curving arc- placing the nylon net horizontally rather than vertical. it lasts for many years and uses, but it does tangle easily when not stretched out. logan's sells it, or used to, but i got mine from pinetree. the holes are about 6" or so. it's very strong, nearly invisible once it mildews down a bit, and easy to clean off vines at the end of the season. not much tying needed- just weave the plants in to start. we have 2 permanent trellises in the garden i plant veggies on, as well as temporary ones that may last a season or 4. we just reconstructed one that we'd had for 10+ years. i also use bamboo teepees that i wrap with sisal or jute in a spiral fashion.

for determinate tomatoes i tend to use these metal supports i bought a while back that you can wrap into triangles or link together to form a fence. i link them, then make the fence zigzag and plant the plants in the inside of the zig. that way the plants support the trellis and vice versa. i do have to tie them up some, as well as weaving the plants in. i also use 4' long pieces of metal that dh grabbed at work and string twine or jute among them to make a framework for determinate maters & other things that need fairly short support. pete's made a few metal type supports (we mostly use the rejects from something else), but they are fairly short. i've been bugging him to make me some of the rebar skinny teepee type you spoke of- they are very pretty.

we have used cedar before, but it was from some small trees we and our neighbors culled, and we used them whole, with bark. it's great for a long lasting structure because it takes a long time to rot. as it ages the birds & squirrels love to peel the bark off in long strips for their nests. i don't know where you'd buy posts, though. as you might guess, we're big fans of trellising stuff to save space.