The best way I've found to keep up with different members on the site is to add them to your contact list. You can see when they're online by viewing your buddy list on the left hand side of any ECCIE page also. To view your list of contacts you just access your UserCP and then select Contacts. From that page you can see everyone you've saved, remove contacts and click on their name to view their profiles.
Adding someone to your contact/buddy list is easy. (see pic below) Click on their profile, click User Lists, select Add to Contacts and then confirm the change on the next page. Thats it.