Scripture4All have a great piece of Greek and Hebrew interlinear bible software for PCs, but that is not much use if you have a Mac or are unable to install software on your computer. However they also have an online offering that will help provide you with a free interlinear both for the Hebrew Old Testament and the Greek New Testament.
It is extremely easy to use. You just select the chapter of the book that you are studying and you can download (or view online depending on the browser you use) a pdf of the interlinear bible.
The pdfs are simply laid out. On the right is the verse in full in English. Then at the left is the Greek or Hebrew words (with phonetic spelling) and the meaning of the word in English. Each verse is dealt with separately, so the pages are very structured.
The disadvantage of the online version is that you cannot drill down and get lots of detailed information on words. The converse advantage is that its simplicity make this a great guide for any chapter you are reading, with perhaps other tools being used when you feel you need to investigate further.