I can get my college email account to work in Microsoft Outlook, but I can't get my Yahoo! account to work or any other email address. Is it possible to make it happen and if so, how?

For yahoo mail you need upgrade to yahoo mail plus to get
the full pop3 service for access to outlook,incredimail,
thunderbird, and others.
And use the yahoo mail servers address (for yahoo.com address)
* Incoming Mail Server (POP3): plus.pop.mail.yahoo.com
Use SSL, port: 995
* Outgoing Mail Server (SMTP): plus.smtp.mail.yahoo.com
Use SSL, port: 465, use authentication
Click this link for yahoo mail pop3 settings
http://help.yahoo.com/l/us/yahoo/mail/yahoomail/mailplus/pop/pop-14.html
http://help.yahoo.com/l/us/yahoo/mail/classic/mailplus/pop/pop-08.html

And for yahoo mail servers address (for yahoo.co.uk address)
* Incoming mail server (POP3): pop.mail.yahoo.co.uk
* Outgoing mail server (SMTP): smpt.mail.yahoo.co.uk
Click this link for yahoo mail pop3 settings
http://help.yahoo.com/l/uk/yahoo/mail/classic/manage/pop-06.html

Or you can try free ypops but it may no longer
work with yahoo since yahoo changed there settings and pop3 address.
http://ypopsemail.com/