There are some sites which provide helpful and significant content (e.g. offer primary texts, peer-reviewed scholarly journal articles, bibliographies. There are also sites which provide well organized links to other sites of substantive value. Although you may not be purchasing anything, caveat emptor is an appropriate caution. You are spending (part of) your life (you call it "time") in the learning process and you don't want to waste it on useless sites with questionable information.

When doing research, pay attention to the institutional sponsorship of the site (there are good independent sites out there, however, usually a site sponsored by an institution is of higher quality than a site offered by a single individual).

Depending on what the site is providing, watch for evidence of active maintenance. Obviously a site with a carefully prepared (proofed) text of Josephus does not need to be constantly updated. Other sorts of sites which have not been updated in more than a year should be treated with care.

With respect to the kinds of sites we would be dealing with on the research side of theological studies, the norm is free access. Sites which try to collect money from users should be treated with care.

Is the author, editor of the material identified? Is there some indication of his or her credentials? Does the site present well (indicating some care in its preparation) or is it garish or poorly organized? Has the material itself been prepared with care or are there errors in spelling and grammar (e.g. "I hope to peek your interest in the main tenants of my moral principals ...")

Disclaimer: The inclusion of a link on this site does not necessarily indicate an endorsement of the contents of that site by this professor or institution. As always critical judgment is expected.