I agree with BPS's comments, although I have to admit we haven't pursued incorporation yet. However, it is on my list of objectives for this year.
The primary reason to incorporate as a non-profit is that it turns your PTO into a legal entity as opposed to a collection of private indiviuals. This lessens the potential liability, especially among the Board members should something go wrong and the PTO gets sued.
As far as the 501(c)(3) process, it's really not that bad. Yes, it's a lot of paperwork and intimidating when you first start. However, that particular branch of the IRS is so helpful it's just unbelievable. Plus, with the Forum as a resource, there are plenty of us who have already done it who will answer questions and share information.
As far as constitutions/bylaws, many are listed on the PTO/PTA websites, and there a lot of those listed under the PTO Management Forum message called "List Your School Website". You are wise to look at what others are using, pick one and customize it. That's much easier that starting with a blank page. Here are some other websites that may help you. Good luck!
Tax Information for Non-Profits
www.mapnp.org/library/tax/np_tax.htm
Frequently Asked Questions on Tax Exempt Status
members.aol.com/irsform1023/misc/faq.html
IRS Forms & Publications
www.irs.ustreas.gov/forms_pubs/fillin.html
Publication 557: Tax-Exempt Status for Your Organization
www.irs.ustreas.gov/forms_pubs/pubs/p557toc.htm
Form 1023 Help
A free website designed to help non-profits with Form 1023
www.form1023help.com/
Application for Recognition of Exemption – 501(c)(3)
ftp.fedworld.gov/pub/irs-pdf/k1023.pdf
Gaming Publication for the Tax Exempt Organization
(Read this if you are 501(c)(3) and plan Bingo as a fundraiser)
ftp.fedworld.gov/pub/irs-pdf/p3079.pdf
Quality 990
(Purpose: to improve the quality of IRS Form 990 reporting by nonprofit organizations)
www.qual990.org/index.html
501(C)(3)
Contributions
www.irs.ustreas.gov/prod/bus_info/eo/contrib.html
Publication 526 - Charitable Contributions
www.irs.ustreas.gov/prod/forms_pubs/pubs/p526toc.htm