Wood

I don't think I've mentioned anything about this for quite some time, but wood slices are one of my favorite parrot items, ever.  An untreated 2X4 pine provides many, many hours of entertainment.  If you have access to a saw and have some skills, they are one of the cheapest and most entertaining items for birds that I've been able to find.  Sometimes I drill them and hang them on wire, but frequently I am lazy and give them to the birds as-is.

Thomas slices them in various widths; the littler guys get more thinly-sliced wood:

I hide a bunch in Calypso's cage every morning and return home to a pile of wood chips.

Even Basil, who doesn't really play with toys (we're working on him!) loves them:

We leave a basket full of them out at all times for Rocky.  When he wants to chew, he wants to chew.  If nothing acceptable is around, he'll use the fishtank, baseboards, or other unacceptable substitutes.  By providing him with easily accessible acceptable wood, everybody wins!