For both original language work and interpreting biblical texts, commentaries are an essential tool. A good commentary will be scholarly, discuss a variety of views, and provide detailed discussion of verses. This page lists guides for selecting commentaries.
You may be familiar with the bestcommentaries.com website. This site has both good and bad points that you might want to consider before using it.
PROs
1. Freely available on the web.
2. A variety of commentaries are listed there.
CONs
1. There are no qualifications for posting on the site--anyone can write anything.
2. There is no sense of "peer review" of the content.
3. Every review is the opinion of the poster.
4. The site is simply a collection of opinions by a widely diverse group of individuals, who may lack theological training.
These negative factors likely outweigh the positive factors but the decision is up to you. Any resources that you use should still be guided by general principles for evaluating possible resources.