Following links are important for those interesting in finding out funding opportunities:
(More links will be added later)

FUNDING OPPORTUNITIES

Register for email elerts:

Main link to get information for all government grants:
http://www.grants.gov/

GrantsNet Alerts:
http://grantsnet.org/funding_news_alert.cfm

Department of Energy:
http://www.energy.gov/news2009/email_updates.htm

U.S. Department of Education
http://www.ed.gov/news/newsletters/edinfo/index.html

U.S. Environmental Protection Agency:
www.epa.gov

National Institutes of Health (NIH):
http://grants.nih.gov/grants/guide/listserv.htm

National Science Foundation:
For general information:
www.nsf.gov

Register to receive regular updates:
https://service.govdelivery.com/service/multi_subscribe.html?code=USNSF&custom_id=823

U.S. Science:
www.science.gov

Institute of Museum and Library Resources
http://www.imls.gov/applicants/applicants.shtm

NASA:
http://nspires.nasaprs.com/external/

Center for Disease Control (CDC):
http://www.cdc.gov/subscribe.html

National Endowment for the Arts (NEA)
http://www.arts.gov/

National Endowment for the Humanities (NEH)
http://www.neh.gov/grants/grants.html

Homeland Security:
https://baa.st.dhs.gov/

Search Tools:
Federal Register:
http://www.gpoaccess.gov/fr/

Federal Business Opportunities:
https://www.fbo.gov/index?cck=1&au=&ck=

FoundationCenter:
http://foundationcenter.org/findfunders/

GSA
http://www.gsa.gov/Portal/gsa/ep/contentView.do?contentId=17943&contentType=GSA_BASIC

Proposal Writing Aids
Federal
EPA
Grant writing tutorial
How to Enhance a Grant Proposal
NIH
Inside the NIH Grant Review Process
http://cms.csr.nih.gov/ResourcesforApplicants/InsidetheNIHGrantReviewProcessVideo.htm

NIH Peer Review Policy & Issues
http://grants.nih.gov/grants/peer/

Resources for New Investigators
http://grants.nih.gov/grants/new_investigators/index.htm

Merit Review at NIH - Tips for a strong proposal (Word Doc)
Zakir H. Bengali, Ph.D., Chief, Biochemical Sciences Review Group, 9/23/02 at U of R

Grant Tips
http://grants.nih.gov/grants/grant_tips.htm

NIAID - All about Grants
http://www.niaid.nih.gov/ncn/grants/default.htm

NINDS - Writing a Grant Application, a Technical Checklist
http://www.ninds.nih.gov/funding/grantsmanship_checklist.htm

NSF
A Guide for Proposal Writing
http://www.nsf.gov/publications/pub_summ.jsp?ods_key=nsf04016

Guidelines for Writing Grant Proposals
http://www.nsf.gov/sbe/bcs/ling/guidelines.jsp

NSF-wide Funding Opportunities:
http://www.nsf.gov/funding/pgm_list.jsp?type=nsfw