Xobni: Learn more about Xobni for Outlook
If you use Microsoft Outlook you are going to love Xobni. (Hint: Inbox spelled backwards). It takes email organization to an entirely new level. I just installed it last week. It runs with Outlook so you don't have to dump anything.
Some of the really cool things I have found it to do are:
1) it searches all your emails and comes up with a bunch of really cool analytic stats such as: a) how many emails have you received and sent to a particular individual, b) what time of day does the person usually send you an email, c) what attachments have been sent from that person, and d) who does that person know who you also know (what is their network). It is really a little scary.
2) it has this button under the person's name. It reads "Schedule time with". If you click it the program looks at your calendar and finds gaps in the calendar over the next several days. It then generates an email asking the person if they are available and lists your available times from you calendar. It is amazing. You can edit the email before it is sent, of course.
It is my favorite price also - FREE. Currently in Public BETA so no guarantees but I have not had any problems with it.