Gmail Yahoo Mail – Adding Yahoo Mail as a POP3 Account

Lifehacker.com just published a trick to increase the frequency of the checks in Gmail.

It's a bit of work to set it up, but essentially you need to ensure that your POP3 accounts frequently get new mail.

Gmail bases its mail-fetching frequency on how often it finds messages in the account when it checks; if the account only gets email rarely, Gmail will check it once per hour. From what I've been able to tell, given a regular rate, Gmail's mail fetcher seems to stabilize at fetching twice as often as mail appears in the account.

See this Google article : "Migrate to Gmail from Hotmail, Yahoo Mail, AOL Mail".
This describes utilities that Google had developed for fetching mail and contacts.