On Screen
When it comes to viewing photos on a computer screen, it really kind of depends on what device you are using. A standard desktop computer screen is going to be limited in terms of viability in direct sunlight. Most aren't really designed for use in those scenarios.
These days, there are a number of personal computing devices that can be used for viewing photos. That includes both tablets in large and small form factor, as well as the myriad of smart phones that pervade the marketplace. When it comes to screens, these devices have really pushed the envelope in terms of pixel density, microcontrast, and brightness. Your best screen for viewing photos on a screen in sunlight is going to be an AMOLED. SuperAMOLED from Samsung is one of the best screen types available for high contrast, ultra bright display that works quite well in sunlight. The next best thing is probably the screen on the Nokia Lumia 920, which while not an AMOLED, is brighter than most screens in full daylight. The Lumia screen also has some of the best microcontrast I've seen, and rivals the iPhone Retina for viewing photography.
Tablets, including iPad, Android, and Windows 8, are all starting to push the envelope quite far when it comes to screen technology. Contrast is very good on all of them. The iPad and Android screens are pushing some insane pixel densities (up to and even beyond 400ppi!) At these pixel densities, again assuming AMOLED or Lumia-like technology, microcontrast is excellent, overall brightness and response time is excellent, and these are probably some of the best devices on the market right now to view photography with, in or out of the sunlight.
Obviously a glossy screen is going to cause more problems with glare, however they also have a high transmission rate. A matte screen will be better from a glare standpoint, however there are tradeoffs both ways. Matte screens tend to use some kind of etching or microprism design to disperse and diffuse light, which is how they eliminate harsh glare. In doing so, though, they also disperse light coming from the screen itself. This had the tendency to reduce microcontrast, which reduces the fineness of detail you can see in a photo. One of the things I love about the Lumia 920 is its excellent microcontrast. Browsing 500px or 1x.com photos on it is a dream...largely thanks to the high-transmission glossy screen. Personally, I am happy to deal with a little glare to get improved transmission (which helps improve gamut) and microcontrast, but it is really personal preference. I have seen tablets and "convertibles" (a Windows 8 term to refer to tablets that can be converted in one way or another to a full keyboarded and moused ultrabook) with both glossy and matte screens, so there are certainly options out there.
In Print
When it comes to print, you have a LOT of options. The three major categories that papers fall into from a surface standpoint are matte, luster, and gloss. Matte papers are flat, they have no shiny surface at all. Luster papers, which include semigloss and pearl papers, are coated papers with semi-reflective surfaces. Gloss papers are obviously highly reflective.
Similar to computer screens, gloss papers have a lot of positive attributes. They usually offer the highest dMax (ink density) as well as the brightest white points. That allows them to be exceptionally bright, with high contrast. They will definitely cause glare in sunlight, so are probably not the best choice.
Luster and matte papers will be better options for prints viewed under direct sunlight. There are a wide variety of luster/satin/pearl/semigloss papers, with different surface textures, sheens, dispersion factors, etc. It is really personal preference which one you choose. They offer great dMax, often offer excellent white point, and can maximize gamut. Matte papers will not produce any kind of glare at all, they are entirely flat surfaces. There are probably more varieties of matte paper than anything else, with different textures, surface smoothness, white balances, etc. They are more limited in dMax, white point, and gamut than luster or gloss as well, but it usually doesn't matter as most prints on a quality fine art matte paper look fantastic regardless (and I've printed on a LOT of paper types, so I speak from experience.)
The key thing for viewing in sunlight is not necessarily matte, luster, or gloss, though. To get the best results out of a print that is to be viewed under sunlight, you probably want papers with OBAs, or Optical Brightening Agents. These are components blended in with the paper fibers. They are designed to convert UV light energy to enhance the brightness and color quality of a print. Paper brightness is the primary thing affected by OBAs. Papers without OBAs rarely get much above 90% on the whiteness scale, and are often much lower. Papers with OBAs can get as high as 98% on the whiteness scale (and some specialty papers might get even higher). This expands gamut, improves global contrast, and really helps make printed photos pop when viewed in direct sunlight.
The drawback to papers with OBAs is that they decay under that very same sunlight. All "archival level" papers, papers which maximize the lifetime of a print, are acid, lignin, and OBA free. All three damage either the paper itself, or the inks printed on the paper, over time. That said, if a print is going to be viewed in sunlight, it is not going to last long regardless. The sun will bleach anything that is kept under it for very long. Prints that get regular daily sunlight can last for as little as a few years before fading, or perhaps a few decades. The use of papers with OBAs won't matter much on that timescale, and they can greatly enhance the print when viewed under sunlight for its truncated lifetime.
Processing Techniques
There are quite a few processing techniques you can use with software to prepare an image for print. Fine tuning white and black points to maximize contrast while ensuring shadow detail is visible in print. Tweaking gamut to manually recover OOG colors. Things like that can be done to maximize the quality of an image in print. Most of the time, such things are not necessary when you use a properly made ICC profile for the printer+ink+paper combination you are using. The ICC profile under a Relative Colorimetric or Perceptual rendering intent, along with automatic black point compensation, will usually take care of all of those things for you. It is rare that you ever need to edit them manually (although tuning white point is often useful for maximizing contrast in print, if high contrast is what you want.)
I can't say there are any specific editing techniques that will help you improve your print for viewing under sunlight.
Some printers, namely Canon and Epson, often have features in their driver or bundled rasterization software to print sample sheets with scaled-down versions of your image printed with slightly different intents and color balance settings. This can be helpful to find the right print settings to use to optimize the appearance of a print for the standard type of lighting it will normally be viewed under.
Additionally, some printer calibration tools offer the ability to generate ICC profiles for different types of lighting. This builds the viewing context directly into the print profile, making it a printer+ink+paper+lighting profile that can be reused over and over to reproduce prints for viewing under any light, including sunlight.
