Is a Shardmind (from Player's Handbook 3) able to speak? Nothing in their traits says they can't, but they have no mouth (in the arts of the book), and well, they have telepathy to backup.
Yes they can, don't ask me how.
PHB pg.32 (emphasis mine)
Languages: You start off knowing how to speak, read, and write a few languages. All races speak Common, the language passed on by the last human empire, and some races let you choose a language (see “Languages and Scripts,” page 24).
Unless shardminds have something in their entry saying they can't speak, the general rule applies and it says that all races presented as playable characters can speak.
Having only telepathy of range 5 and no speaking ability is such a disadvantage since it can't communicate with people far away or talk to people from the other side of a door that if they really had such restriction it would be specified in the their race description.
A creature that has telepathy can communicate telepathically with any other creature that has a language. The other creature must be within line of effect and within a specified range. Telepathy allows for two-way communication.
But really, how do they talk without a mouth?
I have no idea. Maybe the crystals of their eyes/mouth/neck area vibrate and make sound, it's impossible to know unless a designer answer this but it isn't really important unless you want to gag a shardmind. Since you would depend on a designer to answer this and no one from WotC will answer anything about 4e, you can't even ask that in this SE; I suggest to work it out with your DM to create a reason for this if you feel it matters.