Calendar: Google Calendar Sync (free). Can update my calendar on the Pre, or within Outlook, and everything syncs through the cloud.
Contacts: gSyncit. Only $14.99, and it syncs both calendar and contacts (I use it for Contacts only). I recommend it, and you can get it at http://www.daveswebsite.com/software/gsync/.
Tasks / To Do: GQueues (free). Similar to Google Tasks which is at gmail.com/tasks, but more configurable in terms of priorities, sorting, etc. It's web-based, not a downloaded app, so you're syncing to the cloud.
Memos / Notes: Evernote. The weakest solution of the four in that the Pre app doesn't permit sorting & organizing by categories, such as Business, Personal, etc.
Total cost = $14.99, as compared to solutions like Chapura PocketMirror at $40 (which does not sync Memos), CompanionLink at $40, or the Missing Sync at $40 (which does not sync either Tasks or Memos).