Yes, Equity calls its service the Job Information Service - you won't find it unless you log in as a member, and to be a member, you have to hold an Equity card. In that sense, it is not 'free' per se - it is a benefit that is offered to those who pay their union subs. Unlike many other sites, it ONLY carries paying work, although its coverage is disappointingly limited. There are current discussions going on on the Equity forums as to how to improve the JIS so that casting directors will be (potentially) more interested in issuing breakdowns to it - however, you won't be able to access the forum unless you are an Equity member either!
It is true that most subscription and free sites carry the majority of the same ads - this is not least because low budget setups who have few other resources need to maximise the likelihood of their getting a cast together, and it is, therefore, in their best interests to 'carpet bomb' as many sites as they can. This is quite different to how most high ranking casting directors cast - they tend to stick to very limited releases of breakdowns to very specific people. Occasionally, the odd high profile CD/director etc. does turn up casting on online sites, but generally in the hope of getting the cast on the cheap.
CCP always gets my subscription because a) I like the user interface, which is extremely user friendly (and, in fact, should be a model for other casting sites, IMHO!) b) because the forums are an excellent additional feature and c) because I seem to be able to land auditions and jobs from it. I am also a Castnet subscriber - I find they are good at delivering on their promise to vet the breakdowns they send you with a certain degree of specificity, and they seem to have a half decent industry rep, which means many of the jobs offered are of a good standard. Castweb is also a distributor of worthwhile information and updated daily - but it offers no possibility of applying via online channels; you have to write and post letters/CV's etc. to the companies concerned in the old fashioned manner.
All of these sites have significant subscription cost; there are some 'free' sites (or, at least, you don't have to pay for using 'lesser' features) - Mandy.com is like this, but I have always found it correspondingly weak - to a certain extent, you get what you pay for. PCR is, in many ways, outclassed by the online setups, who tend to get the majority of the same information out to recipients quicker, and in this sense it is a relic, BUT it is perhaps too easy to dismiss it totally - it can sometimes feature extremely decently profiled jobs that are worth applying for (though it's true that they rarely pay much). PCR is a real 'luck of the draw' publication, however: you can have a weeks' run where you could apply for every gig in sight, and another which is completely devoid of anything remotely useful to you. As you effectively pay for the issue to be delivered to you once a week (whether good or bad), and once its gone to print it's set in stone (though PCR do have a 'last minute breakdown' online service incl. in the price of subscription) this is probably less efficient than paying, say, a months' fee to CCP, and being able to access new data every day.