[edit 11/17/12 - removed https and link seems to work more reliably]
Microsoft has moved their charity / non-profit price list from it's prior location. Took me a little digging, but here's the new URL for those intereted: http://mspartner.microsoft.com/en/us/Pages/Licensing/Downloads/open-license-charity-estimated-retail-price-list.aspx
As always, use the above link for budgeting then hit up your preferred vendor (Dell, CDW, Zones, CCB, etc) and make sure you get pricing BETTER than what you see above. Never pay retail :-)
If the above link is having trouble here's the complete pricing lineup. http://mspartner.microsoft.com/en/us/pages/licensing/price-lists.aspx This link also has a link to a doc on: Finding answers to common questions about the Microsoft Open License for Charities that enables nonprofit organizations to purchase multiple software licenses at reduced prices.
Other posts on charity pricing = http://jpowell.blogs.com/.services/blog/6a00d8345325d569e200d8345325d769e2/search?pager.sort=relevance&filter.q=charity