Quantum Triviality wrote:Also, when I did REU's I distinctly remember a rule that no students who had graduated undergrad could be in them.
of course there are many other options for research besides REUs...
In any case, QT is right. Work you do the summer before you attend grad school (whether that happens to be the summer after your senior year or not) will do you no good on your grad school applications since you will already know where you're going to grad school before you start that summer's research.
Just make the best of the research opportunities you've got. Grad schools know you only have so much time. If you can do research this summer, do it. If not, just make the best of next summer. If you're at an undergraduate institution that offers research opportunities (or near another institution that offers research opportunities), do some research during the school year.