>I believe there is the Brazilian herb/plant "Guarana" or something
>similar. I can't remember if it is supposed to contain caffeine
>or works as a substitute.
Conventional wisdom (modern herbals) is that the active substance in Guarana _is_ caffeine. My favorite herbal (Graeme's) is a little older (dates to about 1910) and recites that the active substance is in the same chemical family as caffeine with similar effects. My sister swears that Guarana in high doses (what would be high doses in caffeine terms, anyway, like three No-Doz tablets) is a wonder weight loss drug, giving all of the stimulus of caffeine with none of the jitters and digestive side effects. On me, high-dose Guarana has very similar effects to high-dose caffeine (unpleasant).