the Inland Revenue has produced the following pdfs as support for employers considering the use of childcare vouchers:

Employer registration form for you to print (42k)
An employer’s childcare factsheet (72k)
E18 - how you can help your employees with childcare (pdf 56k)
IR115 - Childcare provided by employers (PDF 419K) - The tax and National Insurance rules on employer-supported childcare change on 6 April 2005.
Full guidance on salary sacrifice (PDF 32K)
www.hmrc.gov.uk/childcare/employers-guidance.htm

other useful links…

You may require adobe acrobat to view some files - you can download it here