As I said, you need a newer version of Wordpress do this, but you don't need the latest version to do it (I'm using version 2.2x).
Anyway, here's what you do:
Go to your WP-Admin page
Click the "Manage" tab then the sub-tab "Pages"
Create a page titled Blog and leave the page context blank. By default the page url will be .com/blog (since blog is the page name)
Create another page and call it whatever you want if you want it to be your homepage
Next, click the "Options" tab, then click the "Reading" subtab.
Under the "Frontpage" area it will give you options on how to display your latest posts and what will be your homepage. By default the front page is your latest posts. However you have the option as seen in that are to select "Static page".
Select static page and for "Front page" (your homepage) select whatever page you want, such as your "About" page. For your "Posts page" select the page you created called "Blog".
Now your site will have your homepage as your "About" page and your latest blog entries will show up on .com/blog.
If you have any questions just reply to this thread