In addition to getting the current weather report on the day of a hike, how does one find out if the trails are currently in good shape and what kind of gear may be necessary that day (i.e. crampons)?
Getting trail conditions is region-specific. For example, in New England the Appalachian Mountain Club provides a good deal of trail info. I'm pretty sure there is a web site about trail conditions, but for the White Mountains of New Hampshire you can get trail conditions info directly at the Pinkham Notch visitor center run by the AMC, the National Forest visitor center in Lincoln, and probably various places you can call including the several you could walk into to ask. Every major park or forest has some place you can call or look on the web.
For more obscure places (hiking-wise), it gets less formal. Here in north-central Massachusetts, like in much of the US northeast away from the major hiking destinations, there is a surprisingly large scattering of land open to the public with trails on it. There is no one place to go for info about all of them. Most of these areas are just patches of land with maybe a sign and hopefully a few blazes on the trails. There is no visitor center or any building or any staff, so there is nobody you can call directly and there isn't likely a web site with up to date conditions.
For the obscure local trails, you have to use a little common sense. For example, if you wanted to explore the Harry J Rich State Forest in Groton, which is unstaffed with no facilities, you use a little logic and realize it's conditions aren't going to be that different from a few miles away. For example, you might inquire about the Willard Brook State Park in Townsend. Conditions will be similar enough, and someone there may have even recently been out to the Rich Forest.
Or find out about conditions in the town. Lots of towns have conservation groups with web sites. These don't generally list current conditions since that would be too much work for the volunteers to keep up with. But, there is usually some contact info. To use Groton as the example again, there is the Groton Conservation Commission, the Groton Trails committee, the private Groton Conservation Trust, each with web pages. It doesn't take much digging to find a email address or find that there is a grotontrails email list. Send a message saying you're from out of town and would like to know the conditions, and you'll probably have half a dozen replies by the end of the day. If you want to hike in Littleton or Ayer or Westford instead, dig around there for web sites and contact information. For example, Littleton has the Littleton Conservation Trust private group, and the headquarters for the New England Forestry Foundation are located there. If you can't find anything for Ayer, for example, look at a map and realize that whatever you find out about Littleton or Groton will be pretty close.
These are just local examples that I am familiar with since I live and work here, but this sort of small local patchwork of organizations applies to most of New England, and probably to many other places too.
So the answer for less known places is to dig around for local info and be willing to extrapolate to the place you are actually interested in.
This will depend a lot on the region you are hiking. Hiking in the Adirondacks, for example, trip reports from forums are often useful. There are some general trip report sites, but if the area you are hiking sees a good amount of use, it is likely you'll be able to find a site with specific trip reports for it. Try searching Google for something similar to: