I find it hard to believe your friend doesn't know a single person who will listen to him talk. I think more likely he is afraid to show vulnerability to people he knows.
In my experience I've always become better friends with someone who has shared with me or who I have shared something personal with. Through showing vulnerability, which takes courage, we build strength.
I've also been surprised at how accepting people are when you confide in them. People are much more sympathetic then we think.
That being said here is the national suicide prevention hotline 1-800-273-8255 just incase its an emergency. I know people who have called before it's not a big deal they don't send out police to your house or anything like that, if anything you may have to wait on hold for a while, but the people who work there are saints
I am socially isolated. I can go for several days without speaking to anyone. Sometimes the only speaking I do is the hellos and thank yous to shop keepers.
I find it easy to understand someone who might not know anyone to talk to.
Using a web search engine to find a support service or using Reddit is very different to talking to someone who knows you.
You don't have to be suicidal to get someone to talk to, if you really have no-one you can approach personally. Ministers of religion are everywhere, and this is their supposed bailiwick. You don't have to be religious to talk to them.
Large cities often have some kind of resources where you can see a social worker (who can refer you) or psychologist. The trick, of course, is getting over the initial reticence. Or look for things like depression hotlines - these are sometimes separate to suicide ones.
College didn't work out for everyone. There weren't enough jobs for all of us, now I am in my mid thirties, have no friends, and am unemployable. But you can rest assured that, yes, most people think that I shouldn't exist.
Hello! I believe you are more valuable as a person than the contributions you make through a job. Many people find their self worth through employment, but when you get down to the nuts and bolts of it, employment generally means making money for someone else. This concept of economic slavery causes people who don't fit into the job market to feel like they're not worth their weight.
Your value as a person doesn't have to be defined by your employment. If you open your mind you can find your value as a listener, a thinker, a gardener... whatever.
It is extremely likely that humanity is an evolutionary dead-end that will never spread out from this little rock we're on prior to its eventual destruction (or even more likely, our own destruction prior to that), in which case nobody's contributions will have mattered any more than your own in the long run.
So don't sweat it too much.
But I advise making some friends and making yourself employable because both of those things pass the time pretty well.
There are more than a few people who have done well in the professional world, only to discover that said "value" is a myth. Your value is intrinsic, it doesn't come from any job, any social status, or any amount of money. So, for the record, I think you should exist.
That said, internalizing that message is tremendously difficult. I struggle with it myself.
In the UK, there's the Samaritans helpline, which is completely anonymous; the NHS also help, you can talk to your GP in confidence.
I don't know exactly who to call elsewhere, but as chad_oliver says the helplines are there. http://www.mentalhealthamerica.net/ lets you search for a local support group in the USA.
It's always going to be difficult to pick up the phone the first time, but it is worth it.
Its not really obvious. If you're religious, the local priest / reverend is not a bad bet. They tend to have a training and know a fair number of people. Otherwise, the suicide prevention hotline works for those moments of "I'm alone".
Some of the danger for people is the thought of attracting attention from authorities that could make it all worse. The two suggestions above shouldn't have that effect.
There are quite a few hotlines which have volunteers who are willing to listen. I'm not sure if that's the sort of thing your friend is looking for, but it's certainly better than nothing.
You don't need to be suicidal to call the SF Suicide Prevention line. From http://www.sfsuicide.org/get-help/call-us/: "Trained volunteers are available 24 hours, 7 days a week to listen and help you sort things out. You do not need to be suicidal to speak with us." I don't know for sure, but I suspect other prevention lines are similar.
Join a group/club. Book club, sports club, some sort of tech-related local meet-up group, game club, etc.
Joining an active development community for some opensource project that has primarily online interaction is not as psychologically beneficial, but might be sufficient depending on level of depression/isolation and how it affects you.
