I've gotten a lot of questions about how to sign up for clinical trials of Rember and Dimebon, so here's some information:
Rember - it doesn't look like recruiting for Phase III trials has begun. You can sign up to be on a mailing list for information about the trials by sending an email to email@example.com, or watch for information to be posted on the TauRx site. You can read my post about the Phase II trials of Rember for details.
Dimebon - Medivation (now working with Pfizer to develop this drug) is recruiting patients with mild to moderate Alzheimer's for the Phase III trial of Dimebon. You can read more information at www.connectionstudy.com. Note that if you are currently taking Alzheimer's medicines, you cannot participate in this trial.
The U.S. National Institutes of Health has some good information about clinical trials at clinicaltrials.gov. Scroll down to read what you should consider before participating in any trial.