It's a good idea to see how they list the other bands on the site to get a clue of what text to send them. And unlike business sites that are easy to find with search engines, the likeliness of someone randomly finding your band's site are extremely slim. Only people who already know you will see your site. People who you give the URL to in person, or people who already know the band and search for your exact name to find your site. Some of these sites get thousands of hits a month, and you will gain substantial visitors through those links.
Every link helps.
Remember that some search engines take forever to update or add new links, too. Another thing to be sure of is that all your printed materials contain your web address. Be creative and don't miss a chance to nudge someone to visit. If you can't afford new business cards, write your URL on the back of the old ones for now, and make sure it is included when you get new cards, bios, photos, or anything else. Don't forget to include your e-mail address, too.