Try this article. http://www.babycenter.com/0_sleep-aids-for-new-parents_7932.bc
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I found this…
http://answers.yahoo.com/question/index?qid=20070616185915AA1gXMA
the lady who was picked the best answer is awesome!!! if she answers this question also, give her the best answer vote - hehe!

basically, says that Tylenol PM is fine.
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Just thought I'd throw this out: Ambien is much more effective (I find) than anything OTC, and:

"Excretion of zolpidem into human milk appeared to be very low (less than 0.02% of the total administered dose) in a study of five lactating women treated with a single 20 mg dose of zolpidem. The milk:plasma ratio was 0.13 at 3 hours [3]. The American Academy of Pediatrics considers zolpidem to be compatible with breastfeeding [4]."

http://www.obfocus.com/reference/Formulary/Drugs%20in%20Pregnancy/Zolpidem.htm

…if you'd have to take a large dose of the OTC stuff for it to have any effect, a low dose of Ambien might be a better choice? It is the nursing-safest thing I'm aware of for sleep.
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Tylenol PM is safe but remember it is an antihistamine not really a sleep aid. You can get the same ingredient (Diphenhydramine HCl) in Benadryl and other drugs without the the tylenol.
http://www.kellymom.com/health/meds/cold-remedy.html#antihistamines

Ambien may be safe during lactation, it is AAP approved for use during lactation but it is classed as L3 (moderately safe) by Hale. I avoid anything not L2 or L1

Here are resources for looking up the safety of specific drugs and herbs during breastfeeding:
http://www.kellymom.com/health/meds/aap-approved-meds.html
http://www.pdrhealth.com/drugs/drugs-index.aspx
http://www.safefetus.com/Search.asp

Also during business hours(EST) this is an awesome resource, dial a 10-10 number and it will cost less than $2:

Motherisk's Home Line - (416) 813-6780 - for information about the risk or safety of prescription and over-the-counter drugs, herbal products, chemicals, x-rays, chronic disease and infections during pregnancy. [This is a toll call to our Toronto call centre. Callers may have to wait up to 10 minutes to speak to a counsellor.]

These Helplines are open Monday through Friday, 9 a.m. to 5 p.m. EST

(I know it only says pregnancy but they do breastfeeding too
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Benadryl works best and is safe for baby.
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