I just read an excellent article about continuing research on the effects of Rosemary on memory. Robert Tisserand outlines how researchers have shown subjects to be 60-75% more likely to remember to do things in the future when they inhale Rosemary essential oil beforehand. There is also reference to the ability to better handle mathematics (I could use that!). He also lists historical references to rosemary and memory, including from Shakespeare.
This is definitely worth a read. And a sniff.