Web 2.0 website that will improve my writing?

College is a good place to go to improve your writing skills.

But maybe that's the long way around the bush. I'd look into local community colleges, where you might be able to take a single course or two without paying full tuition. Really, though, this all depends on what kind of writing you want to do. Can you be more specific?

I would like to focus on expository/technical writing.

Every writer in English should read the very short but very good "Elements of Style" by Strunk & White.

If you've got the time:
Expository writing%u2014that is, writing typicaly for long-form journalism purposes%u2014is typically taught in English departments at colleges. Again, look at local community colleges, assuming you're unable to enroll full-time. As far as technical writing goes, you probably would want to look for a course like "writing for scientists" or "writing for engineers" which I know are taught regularly at large universities...but maybe not often at smaller colleges. If the kind of writing you want to be doing is not related to journalism, litterature, or other humanities disciplines, then you might want to go to the Web site for a college in your area, look up a professor in the department most closely related to the kind of writing you want to do, and call or email a professor from that department to ask for advice. Say, "Hey, prof, I know I'm not a student, but could you recommend a way to learn effective writing for people who work with computers and technology?" If you just generally want to improve your writing, by far the best thing to do is either enroll in a basic writing course in the English department or to ask for advice from somone in an English department. That's where writing, generally conceived, is taught.

If you're not feeling very social, check out these texts:

For technical writing, "A Pocket Guide to Technical Writing" by Pfeiffer or "Technical Writing 101" by O'Keefe.
For expository writing, search "expository writing" or similar at amazon.com. Mostly these are teacher's guides, but some might help, assuming you're an adult. Also there's http://www.write101.com/ and similar Web sites...just use google to search for those. There are tons of them.

Hope this helps! Let me know if you have further questions.