I used Joomla! for my sorority's national webpage. Joomla! is completely free (although I've seen webdesign companies advertise a "Joomla! powered site" starting at around $1000). It's a CMS (Content Management System) so updating the content is as easy as using a word processor.
The downside of Joomla! is that it can be tough to customize; although there are a lot of templates out there that look nice -- most of them are not free. The one I used was free...but I spent some serious time customizing the CSS and adding Javascript and graphics. Also, you need to have a "plan" or "map" of the website before you start adding content. Depending on what category you put the content in, determines how it looks on the site...so it's a lot of trial and error if you're learning. And lastly, a lot of the "meat" of the site (like a photo gallery, guestbook, etc.) needs to be supplied by 3rd party extensions...also a lot of time....to test it out and then see how it works/looks. You also need to make sure your web hosting account gives you PHP4 or higher and MySQL databases.
I've worked with several CMS and Joomla looks the most professional and can go live very quickly. Plus it makes things like a member-only login and layout a no-brainer. It may be a little much for a chapter website though.... I think something more simple....like what the Iota Kappa chapter of my sorority did
here might suite a single chapter better (that site is done in Flash).