Some job websites, like Job Search Digest, are aggregators that pull together openings posted on other websites and, if you’re willing to pay for a subscription, give you access to those job postings. I do not recommend such sites. In fact, one way to use such sites for free is to sign up for their free service, which gives you the listings but not the job details (for the latter you must be a paid subscriber), and then simply search the web for the exact job titles you’re interested in. A powerful search engine like Bing will find the source website where the posting originates.
On the other hand, if you’re really desperate to find job openings and/or just lazy, these sites can help. Job Search Digest, for instance, has three separate services: private equity digest, hedge fund digest, and investment banking digest. If you subscribe to the hedge fund service, you get daily e-mails of job postings related to hedge funds. Not all openings are quantitative, and many are posted multiple days. Whether this is of value to you, you’ll have to decide for yourself. Subscription is not cheap, so think twice before you pay for such a service.