I'm the only developer in my company, and am getting along well as an autodidact, but I know I'm missing out on the education one gets from working with and having code reviewed by more senior devs.
Does anyone know of any sites/resources that provide volunteer mentors? I'm looking for some one to review my code from time to time and give me some pointers.
Maybe a charitable SO user?
[.NET, C#, ASP.NET]
I just want to clarify that you realise the business ramifications of this? Showing code outside your company doesn't just leave you liable for being dismissed but might land you in court on criminal charges...
Maybe try some work on a reasonable sized Open Source Project in your poison of choice (language). I'm sure if you started commit code there would be people to review/give you pointers on your work.
I find that posting code here on SO in response to other peoples' questions is a great way to have your code reviewed for free (and very quickly). It's great because someone will usually post better code or a different approach from yours, and their post will usually include reasons why they think their approach is better.
Have you approached this from the other side? Getting your code reviewed does have value but you can also do a lot on your own.
I don't presume to know if you are doing these already but here are some thoughts.
You should read. A lot. That could involve stackoverflow, technical articles, various coding standards, design guidelines and code. From that research you can apply some self critique. What are others doing that you are not doing and vice versa.
Run fxcop against your code. See what it flags. Read up on the rules and see why they exist. Repeat with stylecop. I think these two can add quite a bit of value in terms of reviewing your code.
Go back and look at old code you have written. See if you can find areas for improvement. You can think about design here instead of just standards and style.
To go back to your actual question, have you tried networking? Do you have any .NET (or other technology) user groups in your area? You may be able to find some good mentors there.
I've been in a similar position. I found it had less to do with my code quality and more to do with what my code is doing.
You have tagged this asp.net. Have you tried MVC? If you are the only developer, it should be easy to find an excuse to use it.
What is your code coverage like? Have you tried written unit test? Have you tried a mocking frame work? Dependency Injection? Even Linq-Sql! (or Linq to anything!)
Then there are best practices for MVC, Unit Tests, Mocking Frameworks.
Others have already suggested Open Source. Jon Skeet has just started the C# version of JodaTime. Give that a try.
I think our industry is a contact sport, and you need always need to be proactive or you'll get blindsided...
Check out your local .NET Users Group. You can usually find some good local developers there to talk code with.