I'd like to say a few words about self-publishing, based on my own experience so far, since it's something that is simultaneously remarkably easy and surprisingly complicated.
It's obviously a whole lot easier than it would have been just a few years ago, now that ebooks are something that a large proportion of the potential audience for your work is reading on a regular basis. The Kindle store and its equivalents allow you to turn your manuscript into something that is available instantly to readers around the world. There are no upfront costs for printing books, and all the logistics are handled by the online store. Certainly as far as the Kindle store is concerned, publishing is in principle as easy as uploading your manuscript and cover art, typing in the basic details and choosing a price, and I'd be surprised if any of the other major stores are any different.
I say 'in principle' because of the one element of the process so far that has been surprisingly complicated: the tax requirements. The issue is that Amazon is apparently required by the US to withhold a percentage of all royalty payments on the basis that they might be subject to US income tax. I'm a UK citizen and resident, and so I pay income tax in the UK. Fortunately there's a double taxation treaty that means I don't have to pay it in the US as well, but unfortunately it isn't quite so simple as checking a box on the Kindle store.
Amazon does a good job of helping with at least part of the process, but the first step is to obtain a US Taxpayer Identification Number, and for that you're on your own. I know that there's a lot of conflicting information out on the Internet, both from various blogs and from the IRS themselves, but this is my experience anyway.
You can apply for either an Individual Taxpayer Identification Number or an Employer's Identification Number, but I chose the ITIN since I'm an individual and don't employ anyone. You need to complete Form W7 (available here). The official instructions for the Form are not amazingly helpful, but there are a variety of guides available on the web. You also need to send off confirmation from your publisher that you will be receiving royalties, but helpfully Amazon produces a standard letter for your to fill out and print.
The most confusing part is the identification requirement. Now, you can send off your original passport if you want, but since it takes about eight weeks for them to reply (you have to post the form to Texas) I'd imagine most people don't want to do that. Instead you can send a copy of your passport, but not just any copy: it needs to be properly certified. I've heard it said elsewhere that you need to bring it into your local US embassy to be copied and signed, but when I looked there weren't any appointments at the embassy available.
Fortunately that's not actually necessary. The rules say that you can have the copy approved by the agency that issued your passport. Well, the UK Passport Office won't do that, but it turns out that there is a UK Legalisation Office whose function turns out to be much less interesting that the name would suggest. What you need to do is get a solicitor to copy the passport and certify it in accordance with the Legalisation Office's rules (which is much easier if you happen to work with a bunch of them like I do). Then, you pay the £30 fee on the Legalisation Office's website, fill out their form and send the form, receipt and copy passport off to them. After a while it returns to you with a little bit of paper glued to the back, which is apparently what is required for it to be recognised abroad.
Once you've got that you can send everything off to the IRS, and at that point it just becomes a matter of waiting. I've read about other people who have had their application rejected several times for errors on the form, but when I finally heard back from the IRS it was to confirm that my ITIN had been issued.
After that, all you need to do is answer a series of questions on the Kindle Direct Publishing site, which automatically fills out your form W8 and (mercifully) sends it off to the IRS electronically. Then, more waiting.
Still, it's really not that difficult, and the end result is well worth the hassle. If you're confused about anything just ask me - I might not know the answer but I can certainly make something up.