In advance of iOS 5, Apple has released Find My Friends, a location sharing app similar to Glympse. As the name implies, Find My Friends will let you locate your friends on a map. It'll also let you share your location so your friends can find you.
For those concerned about privacy, the location sharing feature can be turned on permanently or only temporarily which is great for when you want your friends to meet you while you're eating dinner at a local restaurant, but not when you go home. It's also conveniently integrated with the built-in contact and map applications so you can find your friends and generate a route to meet up with them.
You can install Find My Friends by visiting iCloud.com on an iPhone running iOS 5. You can also download it from the App Store.