I needed my envelope to get there in three days, with a tracking number, signature arrival verification, for as cheap as possible. Mail Plus got me in and out in less than a minute for $7 bucks.
Pros:
Convenient location off Southern/McClintock
Variety of shipping options
Mailboxes available
Next door to Back East Bagels
Cons:
Cash only for less than $5
The only reason for less than 5 stars was that the cashier opened 10 minutes after 9am without much of an explanation or apology for being late. I don't mind waiting a few extra minutes, but the customer service just wasn't THAT great. Otherwise, I like these kinds of Postal stores (Postnet, too) as a great alternative to the Post Office or a brand name shipping outlet (UPS, FedEx, etc).