One space after punctuation is proper:
http://spider.georgetowncollege.edu/t3/wsr/csc120/wp1spa97.htm
http://www.grammarbook.com/punctuation/spacing.asp
http://www.irvingisd.net/technology/documents/Keyboarding%20Guidelines.pdf
http://www.tcet.unt.edu/START/instruct/general/kb-dks.htm
http://www.sau16.org/resources/keyboarding/kbstrategies.htm
http://www.indstate.edu/upubs/editstyleguide.htm
http://desktoppub.about.com/cs/typespacing/a/onetwospaces.htm
Google Search for "spacing in punctuation"
1 space is preferred, but 2 spaces is still acceptable:
http://www.mla.org/publications/style/style_faq/style_faq3 - Modern Language
Association
http://www.bham.wednet.edu/technology/TechWeb/Keyboarding/KBTchrTips.htm
http://www.writersblock.ca/tips/monthtip/tipjul97.htm
http://www.mtdaily.com/mt1/options.html
http://www.amazon.com/gp/product/customer-reviews/
- Mavis Beacon Keyboarding Software
Professional Guides / Documents
http://www.yale.edu/seas/SEASStyles2004.pdf
- From Yale University. Endorses use of "En Space" (A space with a
width equal to that of a figure in a given typeface and nominal type size) after
punctuation that ends a sentence
http://istpub.berkeley.edu:4201/style/
- Cal-Berkeley IST Editorial Style Guide -Use one space
(not more) between words and between sentences.
http://extension.dce.harvard.edu/2004-05/ext04almgt.pdf
- Harvard University Document in .pdf form uses one space between punctuation
The overall conclusion I get from the following pages are to use only 1 space after punctuation, but using two spaces after punctuation can be still acceptable. The decision on what is acceptable is dependent on the individual business, institution, or instructor.