The Overview Bible project also has a nice summary of the Gospel of Matthew.
The Bible Gateway is a good place to begin a study. Pick a chapter in which you are interested (such as Matthew 1) and then along the right side of the page, click on "Study This". A variety of commentary options will appear, some old, some new, some free, some not.
On Wikipedia are chapter and verse studies for most of the New Testament! For example, here is Matthew 7, both chapter and links to verses.
But, frankly, one should spend most of one's time on the original source, the Scriptures themselves. The commentaries are for the curious, after reading a bit in the original Bible chapters ... which we will try to do tomorrow!
The Blue Letter Bible has a study guide on Matthew. It begins here.
Bob Utley, a pastor out of East Texas (where I'm located now) has a nice overview of various passages from the Bible. Here is his introduction to the Sermon on the Mount. Bob's accent meets the stereotype of the southern televangelist, but his understanding and communication of bible passages is much better than that.
On a different direction, here is the Wikipedia page on the Renaissance painting of Jesus calling the tax collector, Matthew, to be his follower. The gospels were the source for much of medieval and Renaissance art.
While searching Youtube, I found a four hour (!!) adaptation of Matthew as film. Personally this is not for me (I'd rather read the whole book – in the KJV – than watch this very slow moving film!) but it shows the things one can try to do with Bible Study.
Tomorrow we return to Matthew's account of the Sermon on the Mount.