Dr. Mercola says:
Safe sun exposure is essential for optimal health, but incorrect exposure can raise your risk of skin cancer while not providing any health benefits. Sunburn should be avoided at all cost. Detailed guidelines are provided for safely increasing your vitamin D stores through proper sun exposure are included.
While sunlight is composed of about 1,500 wavelengths, UVB is the only wavelength that will produce vitamin D when hitting unexposed skin. UVA’s increase your risk of skin cancer and causes photoaging of your skin. Therefore, it’s important to determine the ideal times of year for safe and effective sun exposure, and avoid exposure during times that UVB rays are not present. Instructions are included.
Vitamin D3 is an oil soluble steroid hormone that forms when your skin is exposed to UVB radiation from the sun (or a safe tanning bed). When UVB strikes the surface of your skin, your skin converts a cholesterol derivative into vitamin D3. It takes up to 48 hours for this vitamin D3 to be absorbed into your bloodstream to elevate your vitamin D levels. Therefore, it’s important to avoid washing your skin with soap after sun exposure.
In case you do develop a sun burn, immediately apply raw aloe vera. It’s one of the best remedies to help accelerate skin healing.
From a health perspective it doesn't make much sense to expose your skin to the sun when it is lower than 50 degrees above the horizon because you will not receive any valuable UVB rays, but you will expose yourself to the more dangerous and potentially deadly UVA rays. UVA's have a longer wavelength than UVB and can more easily penetrate the ozone layer and other obstacles (like clouds and pollution) on their way from the sun to the earth. UVA is what radically increases your risk of skin cancer and photoaging of your skin. So while it will give you a tan, unless the companion UVB rays are available you're likely doing more harm than good and should probably stay out of the sun to protect your skin.
Link: Beyond Wikipedia: 20 References You Can’t Do Without | Mindful Ink.
Bartleby – This site has far more than quotes, you can find full texts here as well – poetry in particular.
Citizendium – This is supposed to be the more “professional” Wikipedia. So far it’s not really taken off, but the information here is often a bit more “elite” but usually not as detailed.
Answers.com – Answers.com is a sort of “commercial” Wikipedia. It makes use of the info on Wikipedia, combined with many other reference sties, to become a one stop shop. It also has a mobile site that I tend to use a great deal.
ePodunk – If you’re looking for information regarding a city or place, it doesn’t get much better than ePodunk.
Encyclopedia Britannica – I know it seems awfully “old school” but this site is an excellent source of information and much more authoritative than Wikipedia.
Scholarpedia – A step up from both Wikipedia and Citizendium in terms of scholarly respectability, it doesn’t have nearly as much information, but the articles have all been written by experts with peer review. An academic paradise!
Okay, two sources that your college probably gives you access to. If you aren’t a student, sorry… but these are too good to ignore. You’ll need to see your local school librarian to see how to access these (or you may have a library website you can access it through.)
JSTOR – You know all those stuffy journals around your professors office? And those articles in your course packets? This is pretty much that. For research it enormously useful.
Oxford English Dictionary – The definitive resource when it comes to the English language. Not just for English majors, the OED (as it’s known) is useful for almost anyone in the social sciences.
Wikiseek – When you absolutely, positively, must have the real thing – WikiSeek is Wikipedia with a better search engine. I would also suggest WikiMindMap for when you’re trying to get a better holistic grasp of a subject.
References for Specific Disciplines
Online Education Database – This is a strange site, and I’m not quite sure what to make of it – but this link lists over 100 specific search and research tools, often relevant to specific subjects.
MathWorld – if you have the great misfortune of having to take math, then this site can be of great help. Everything mathematics from Geometry to Calculus is covered by this site in great detail.
GeoHive and Fedstats – These are both statistics sites, so if you need to know how many people. Fedstats allows public access to public agency statistics. Geohive is a bit cooler, primarily providing global statistics (gender populations, coal reserves, etc). I know, it’s so exciting I can’t stand it.
Theoi and Encyclopedia of Mythology – Both excellent resources on the subject of mythology and ancient religions. This is useful information all across the humanities.
Glossary of Poetic Forms – This will help you get through that English Literature class. You too can know the difference between a Canto and a Cento.
Now, if you’re in my fields – these next three are excellent resources.
Stanford Encyclopedia of Philosophy and Foldop – Both of these are excellent sources on just about anything philosophy related. I use the Stanford site all the time.
Religion Online – If you are a scholar of religion this is an excellent, excellent resource filled with many primary texts.
via Dr. Mercola