Joel Spolsky has a really good article on this topic. The quick summary is that there's two types of Hungarian notation that are used in practice.
The first is "Systems Hungarian" where you specify the variable type using a prefix. Things like "str" for string. This is nearly useless information, especially since modern IDEs will tell you the type anyway.
The second is "Apps Hungarian" where you specify the purpose of the variable with a prefix. The most common example of this is using "m_" to indicate member variables. This can be extremely useful when done correctly.
My recommendation would be to avoid "Systems Hungarian" like the plague but definitely use "Apps Hungarian" where it makes sense to. I suggest reading Joel's article. It's a bit long winded but explains it much better than I could.
The most interesting part of this article is that the original inventor of Hungarian notation, Charles Simonyi, created "Apps Hungarian" but his paper was horribly misinterpreted and the abomination of "Systems Hungarian" was created as a result.
