There are at least five kinds of forms that most affect legal practice - (1) the kind published in Form Books that publishers sell to law firms and law libraries, (2) the kind produced by commercial publishers and provided individually either free or for-fee for the use of lawyers; (3) the kind sold to the general public for basic legal matters and (4) the kind written by courts, administrative agencies, etc., that lawyers fill out and submit to the court, agency, etc. and (5) sample documents actually used in the course of legal practice.
1. Form Books: Form books contain sample forms that lawyers can use as models for drawing up contracts, pleadings, and other documents in the course of their work. There are several kind of form books, but generally they are either business-related or practice related. Many form books are published as multi-volume sets.
The largest form book sets try to cover all the major business subjects or all types of litigation for all jurisdictions. Of these, American Jurisprudence Legal Forms (business) and American Jurisprudence Pleading and Practice Forms Annotated (litigation) comes first to my mind. Together they take up a whole book case in print; they are also available on Westlaw (AMJUR-LF and AMJUR-PP, respectively). Lexis offers Rabkin and Johnson's Current Legal Forms (business) and Moore's Federal Litigation Online Forms (litigation).
Some form books are written specifically to satisfy situations created by a state's statutes. For example, Bender's Forms for the Consolidated Laws of the State of New York Annotated is written and organized to compliment the laws of New York State.
Some state-specific form books are practice-oriented. They are written to assist litigators in a particular jurisdiction, and hence they are written and organized according to the stages and litigation procedures of that state. The Carmody-Wait Cyclopedia of New York Practice With Forms set serves this purpose in New York.
Some form books are subject-specific. Popular corporate & securities-related Form Book sets include Rabkin & Johnson's Current Legal Forms, Contemporary Corporation Forms, and Fletcher Corporation Forms Annotated. Some treatises include forms, though you could never tell by the title; for example, Mancoff & Weiner's Nonqualified Deferred Compensation Arrangements provides a form for just about every type of arrangement covered.
If you are looking for basic forms for laymen, NOLO publishes several, including 101 Forms for Personal Use.
Generally I've just looked in the indexes of the form books in my library, but I've also used Indexmaster to find books with specific forms or searched the master database of form books on Westlaw (use the "FormFinder" for the most forms; use FORMS-ALL to search forms and discussions of forms). If that doesn't get you what you need, search the sources listed in the "Legal Treatises" entry.
2. Commercial Forms Collections: Some Web sites feature free forms collections including LexisNexis Communities and the 'Lectric Law Library's Form Room. The subscription-based ALI-ABA Forms Library taken from ALI-ABA course outlines, books and journals and includes information about using many of the forms.
Blumberg Legal Forms sells subpoenas, notices, contracts, leases and other forms for use primarily by attorneys. Most Blumberg forms are designed for use in a particular state.
3. Direct-to-Consumer Legal Forms: Some companies publish legal forms for sale to the general public. These generally concern some kind of transaction where the parties prefer not to hire a lawyer such as generic wills, uncontested divorces, deeds and leases. For example, SmartLegalForms.com sells forms to non-lawyers who want to do their own legal drafting. LegalZoom and Rocket Lawyer are popular alternatives to hiring attorneys.
4. Government Forms: Courts, administrative agencies and other government bodies generate an astonishing number of forms. You can generally find these forms on the relevant web court/agency web site site or by contacting the relevant court/agency. Links to court forms are posted by Justia, LLRX and FindLaw. Also, most Federal forms are posted by the GPO or Forms.gov.
5. Sample Document Databases: In many cases a practitioner may find a better "form" by searching a database of documents actually used in the practice of law. For example, Lexis Securities Mosaic, LIVEDGAR and other SEC filings databases are an excellent sources for sample SEC filings, and the exhibits can serve as model agreements. Lexis and Westlaw offers databases of sample pleading, briefs and motions. To distinguish, Lexis editors select the documents for their databases, while Westlaw includes all the documents they can download from court Web sites.
For more specific information, check out the entry for the particular court, agency, or subject in question.