yes..there is a really cool feature under the people widget to send the vCard to someone, either by mms, email or BT. Just go to your contacts, long press the contact name and it gives you an option to send contact as vCard. Press that and then it gives you the option of sending by mms, mail or BT and it also gives you an option of what parts of the vCard to send, you can uncheck everything except the phone number if you want...or you can send everything including your notes on and photo of the contact.
edit: I reread your question and I think you were asking for something different than the vcard although the vcard I think might suit you as well, especially if you are interested in giving more info on the contact, such as "plays a mean cello" or " "can only work on Saturdays" etc. But to just copy the phone number so you can paste it in an email, you can do that to. Open the contact in the ppl widget....scroll to the bottom and hit the edit button....long press on the phone number you want to copy....select copy all....then go and paste it into the email you are sending. this could be a tedious process if there are a lot of phone numbers so maybe someone else knows a better way around this.