Hi! I've been into calligraphy for a long time, and I get a lot of lettering ideas that way. You might check out this book: The Calligrapher's Bible. It's like a library of different calligraphy hands through history. I look through it for ideas when I want to change up shapes and proportions, or make a design that looks like a particular time period.
However, it sticks mainly to traditional lettering and is somewhat basic, so it won't have much to help you with really modern hands or "funkyness". It also doesn't have a lot of instruction if you want to learn calligraphy. But it's a good place to start if you're looking for a base alphabet design.
Calligraphy does a really good job teaching the STRUCTURE of letters and spacing and design--just like the basic shapes teach the structure of drawing. It's tough to learn a calligraphy hand really well, but if you learn one or two I really think that carries through all later lettering and design work. Seems to help develop a sense of how to toe the line between legibility and inventiveness.
Hope that helps! 