JumpFuck

Brainfuck, but with some differences:

&   Replace the jump point whose ID is in the current cell with the current jump point, and change the current cell to 0 if we come from & or the argument if we come from %.
 * Unbounded cell size. (already done by many BF interpreters)
 * Automatically expanding tape. (ditto)
 * An extra block of memory (also automatically expanding) containing jump points.
 * Two extra commands:

%   Jump to the point whose ID is in the current cell, using the next cell as an argument.

This makes it far easier to compile to.

Infinite loop
(Admittedly, you don't actually need jump points to do this.) +&>+++++++.<[-]+%

Implementations
weave.rb interprets JumpFuck with the -j flag.