Today we're just getting 3 short letters, two by "John", one by "Jude." The letters are so short, there aren't even chapers. Just a few short verses in each one. Both 2nd and 3rd John seem to be written to individuals, one to a noblewoman and her children, the other to Gaius. I'm a little suspicous (might I say) of the noblewoman. Perhaps the reference is to a congregation, as often churches are referred to in the feminine. Just a thought.
In both cases, the theme of loving one another continues in both of these short letters. As well, the letter writer wants to warn of people who don't believe that Jesus really came "in the flesh." Some teachers of the time believed that Jesus only "seemed" to be human, and therefore could not have really suffered or died, either. Third John also wants to commend one leader and criticize another.
Both positive community habits (the habits of love) and warnings about false teachers and teachings form the core of both of these letters.
The letter of Jude is also concerned with false teachings and teachers. Listen to what Jude says about some teachers: "They are waterless clouds carried along by the winds; fruitless autumn trees, twice dead, uprooted; wild waves of the sea foamong up their own shame...." powerful words. You get the feeling that Jude really really doesn't like these people, and they have been infiltrating the community's "Love Feasts." (It's an interesting glimpse into the life of the early church; we don't have "Love Feasts" any more -- they were probably communal meals of some sort.)
But for all of the harshness of the Letter of Jude, I love these words of closing: "Have mercy on those who doubt. Save some by snatching them from the fire."