Is there anyway I can set up a mailing list using the blackberry or my bwc?

Like I have a list of 20 e-mails, and I always send out group e-mails to these 20 people, so is there a way to make a list of them somehow in the blackberry or the bwc client?

Yes. You can create a distro list within the Contacts on your device.

Go to Address Book. Click the wheel and select "New Group." Next to "New Group" type the name of your new group. Then click the wheel and select "Add Member." Select the contact to add from your address book. If there is more than one email address in that contact's info it will let you choose. Select the email address and click continue. Repeat the process until you have added all contacts you want in your group.

Hope this helps,
John