I've seen quite a few of my sites rise very substantially in the serps of late and the only obvious change that I can perceive is a dmoz listing. What is the view here, assuming that 'trust rank' is becoming a factor in algos, of the value of a dmoz link and also is it worth paying for a Yahoo directory inclusion. Are there any other directory listings that appear to cause marked inprovements in position?
Assuming Trustrank is important. A listing in dmoz.org gives you a link in directory.google.com I don't think there is a domain which google trusts more than google.com So, dmoz makes a significant difference.
Also, I've noticed that the correct link in Y! (I think that it depends much on your category) makes a big difference. In my travel related sites, competitors with old links in Y! directory are hard to beat in Google.
Other than those, I like botw and niche directories.
Trustrank may be one component of the issue. But, on a more global scale, Google relies on links to rank sites. Everything Google does to combat abusive artificial link scams, are going to especially impact link pages, whether or not those pages are set in a matrix of other hierarchically linked link pages (i.e. a "directory".)
Likely, these days, link aging is a big factor. And the major directories have the prototypically natural pattern of link ages.
assuming that 'trust rank' is becoming a factor in algos
I would say it is safe to assume that 'trust rank' is a factor. And why wouldn't those listings play a role?
The editorial control over the listing is a nice vote for the authenticity of the content. It would logically follow that "smart spiders" would view quality directories as a feeding ground for quality content.