Here are some resources we've often liked to share with clients on the topic of how to get their sites noticed now that we've got them out there on the Internet.  The following are links to organizations that offer great tools or are documents with tips compiled by experts in the field (i.e. not us).

1. http://seo.grassroots.org, free webinars for non-profits
2. http://www.google.com/grants, some of my colleagues highly recommend paid advertising, and that you apply for the Adwords Grant as a means of achieving it, though it can take many months to become approved
3. http://website.grader.com or http://analyzers.pearanalytics.com - fun tools that gives some useful tips
4. A Google SEO starter guide (attached)

We also found this great image from an article on SEOmoz that sums up what it takes to optimize a webpage for search engines.

Source: SEO moz

Key elements:

• Carefully selected keyword, in this case: "chocolate donuts." For this example, Mary's Bakery would selected this keyword to target based on research from their Google Analytics data and free tools such as the Google Keyword Research Tool.
  
• Keyword in page title. You can change your page title in the Advanced Parameters section of each Menu Item in the Menu Manager.
  
• Unique meta description featuring the keyword. This text should be under 140 characters and compelling as it is often the description that shows up beneath the title on the Search Engine Results Pages (SERPs).  
• Keyword in Page Title. Your Soapbox site automatically adds headings to this so you don't have to.
  
• Keyword used 4-6 times in page content including at least once in the first 50-100 words. This lets search engines know that this page is really about chocolate donuts and is highly relevant to this term.
  
• Photo of chocolate donuts with the keyword in the file name itself and as the Alt tag. You can set the Alt tag when you add a photo to your content article using the Image Manager.
• Keyword used in Search-Engine-Friendly urls (http://yoursite.org/keyword). Your Soapbox site automatically sets up your SEF urls. You can change the text for each page in the 'Title Alias' field beneath the Page Title when you are editing an article. 

How much will this really help/What if I've optimized my pages and my site still isn't ranking highly on search engines?

On-page optimization is only one aspect of the total package of elements search engines use to rank sites. SEOmoz estimates that it accounts for about 15.04% (see full article). The rest is determined by a variety of factors including how long your domain has been registered, general trust of your domain (automatic bonus .gov, .edu and .org domains!), inbound links to your website from trusted sources, how other sites link to you (the text they use), etc. 

Source: SEO moz