Harmonica Resources
If you have made it to intermediate level, then you should reward yourself with more stuff. Here are my recommendations:
1) More Harmonicas
You probably know already that music is played in a variety of keys, with a different harmonica usually needed for each key. I was first told this at an outdoor festival in New Zealand in 1978, advice for I which remain forever grateful. The following keys will be sufficient for most situations: A, Bb, C, D, F, G. Buy a harmonica case to keep them together, I recommend this one. Some are designed to be worn as belts. I don't recommend these. You generally need only one harmonica at a time, the others can stay out of the way by your feet.
2) Harmonica Albums
Your collection has no doubt grown. Here are some more suggestions:
1) Hollywood Fats Band: West Coast blues featuring the legendary Hollywood Fats on guitar and Big Al Blake on harmonica and vocals. For me, this is one of the all time great blues albums.
2) Smokin' Joint - Kim Wilson: Kim Wilson is generally considered the best of the current blues harmonica generation. This live album shows why.
3) Swingin' Easy...Hittin' Hard - PT Gazell and the Side Effects: Very few diatonic harmonica players attempt jazz. This is a recent and stunning addition to the repertoire.
4) Midnight Special - Sonny Terry and Brownee McGee: Sonny Terry was probably the best known traditional acoustic blues player. All harmonica players should be familiar with his music.
5) Muddy Waters The Definitive Collection: Muddy Waters was the leading Chicago Blues player. These recordings feature classic early Little Walter.
3) Books
Harmonicas, Harps, and Heavy Breathers - Kim Field: The great figures of the harmonica world are profiled. A passionate and inspiring book.