If you need something free/opensource, there’s not many options. When you like it old-school, you can give Knuth’s companion to TeX MetaFont¹ a try.
Then there’s FontForge², which is by far the most evolved, feature-heavy project, but until recently had bad UX/UI and was a pain to install and run on OSX. It seems, that’s changed, though.
FontLab³ still is the type design “industry”’s de facto standard font editor, but development lags behind, and it’s quite expensive for a hobby project.
There are a few other proprietary offerings, notably the DTL FontMaster⁴ tool suite. But Glyphs⁵ seems to be going the winner, steadily taking over market share from FontLab.
If you like scripting your designs (esp. in Python) you should definitely try RoboFont⁶.
When you’re looking for volunteers/collaborators on your project, then do check in at Typophile⁷. For over a decade, it’s the principal outlet for all things type and type design: on the fora you’ll meet some very knowledgable experts always willing to help.
Since you mentioned punctuation, I suppose you’re familiar already with the _Shady Characters_⁸ project (and its companion book⁹). As for a detailed history, I can highly recommend Malcolm B. Parkes† authoritative monograph on the subject, too.
¹ http://en.wikipedia.org/wiki/Metafont
² http://fontforge.github.io
³ http://www.fontlab.com/font-editor/fontlab-studio
⁴ http://www.fontmaster.nl
⁵ http://www.glyphsapp.com
⁶ http://doc.robofont.com
⁷ http://typophile.com
⁸ http://www.shadycharacters.co.uk
⁹ Keith Houston, Shady Characters: The Secret Life of Punctuation, Symbols, and Other Typographical Marks. W. W. Norton, 2013.
† Malcolm B. Parkes, Pause and Effect: Punctuation in the West. University of California Press, 1993.