When I write about and refer to Shakespeare, I have three texts that I'm usually working from. For the plays I use The Riverside Shakespeare; not the latest version, but the one that I bought in college and lugged up and down Orchard Hill faithfully for several years. For the sonnets, I use the Riverside, and I also use the Arden version edited by Katherine Duncan-Jones, and a Yale University Press version edited by Stephen Booth.
The Riverside Shakespeare is my go-to, desert island, collected works of Shakespeare, mostly because it's the one I happen to own, and those suckers are expensive. It does its job, anyway, with enough material and notes to get you by until you level up from amateur to professional scholar, and you can certainly supplement it with other texts if need be.
Since I'm currently taking a closer look at the sonnets, I've found the Riverside version a little inadequate to the task. The notes are very simple and straightforward word and grammar definitions and explications, and not quite as crunchy as I'd like. Thus, the other books:
The Arden version has a lengthy introduction with biographical information and speculation, and I like how it's presented. Each page has one sonnet, with the opposite page dedicated to the notes. The notes themselves present Duncan-Jones' gloss of the sonnet, and detail about the probable meanings of words and phrases, historical and scholarly context, all that kind of thing.
The Booth version is the most overwhelming and difficult, and therefore my current favorite. The presentation is a little annoying: on the right-hand page is a reproduction of the Quarto text of the sonnets, and on the left-hand page is the same sonnets, only modernized. This is great, because you can analyze the originals and decide for yourself if you like the editor's decisions, but it's horrible, because the sonnets get chopped up between pages and you have to flip back and forth between the poems and Booth's notes.
And, oh! the notes. There are 133 pages of sonnets (that's each one twice, remember), and 403 pages of notes. Booth explains in his preface, "All of us were brought up on the idea that what poets say is sublime -- takes us beyond reason; my commentary tries to describe the physics by which we get there... The notes to this edition attempt to indicate not only what words mean but when they mean it; the notes try actively to discourage analyses that treat syntax as if it existed in a static state." They are dense and sometimes hard to read, but also often brilliant. Unfortunately, not only do you have to flip back and forth from the sonnet to the notes (which, if you were ambitious, you could overcome by memorizing the sonnets), but the notes themselves are also very inter-referential, and you have to go flipping about all over the place if you want to get all the references. If someone were to put the whole thing up on the web, it would be genius.
(Okay, I admit to having developed something of a geek crush on Stephen Booth ever since I read the chapter about him in Ron Rosenbaums' The Shakespeare Wars, but, really, his work on the sonnets is good.)
There are also several versions of Shakespeare on the web, some of which sites I've linked to in the sidebar. I'm not very good at reading anything longer than a page or so online, so I tend to skip those for the most part, although they're good for quickly looking up a line or speech or whatever. And, speaking of longer than a page or so, this is starting to push it, isn't it? Next time: the dedication that launched a thousand conspiracy theories.