I should have given a few more details.
This is taping signal, hooking it to my prototype board.
I linked the beagleboard as example as I work with it right now, but I had this issue with different boards (arduino, raspberry, TPM header on PC motherboard...).
The interposed board is the "clean" solution, but I would need to make one for every header I use. I was looking for something modular. I guess I can try to build something for a few pins that I can put side by side.
I guess you mean your intent is
tapping into the signals on the connector.
You mention hooking signals to a protoboard, so I guess this is for a purpose more permanent than just test and diagnosis, but less formal than creating a product.
I think making a board with a stackable connector, that routes the traces out to the side of the connector, is a robust way to go. And if you make it in some convenient length, you can combine two or more to serve a longer connector, or snap or cut it off to serve a smaller connector, or complete a long one.
On such an "interposer" board you'd have to make sure that the ends are tight enough to allow successive interposers arranged end-to-end to continue the pitch of the pins -- perhaps that's obvious!
In googling for "stackable header connector breakout board", I was surprised not to see exactly that sort of thing readily available.
A lower-tech possibility is to simply get some stackable connectors and solder them to a protoboard -- the type with a regular array of individual plated-through holes. That gives you a board and connector assembly that can interpose between the two existing boards. You can then use thin wires to connect to the pads of the pins you want to tap into, and route those wires to wherever you like on your prototype circuit. Wire-wrap wire is a good candidate for this sort of thing.