For social/networking I use the following:
• SocialScope for twitter and Facebook (http://SocialScope.net or @SocialScope on twitter)
• Facebook application for BlackBerry
• Viigo for all my RSS feeds (http://getviigo.com or @Viigo on twitter)
• Bit.lify (URL shortener for BlackBerry directly from your menu)
• Xing application for BlackBerry (http://xing.com or @xing on twitter)
• GyPSii (http://GyPSii.com or @GyPSii on twitter)
• WordPress Wicked App from ScreamingToaster (http://screamingtoaster.com or @Izabel_Idris_ST on twitter)
• Tumblr for BlackBerry
• Email for blogger (although ScreamingToaster are working on integrating blogger & Typepad blogs with their awesome application)
• SnapScreen or ZonaSnap (screen capturing)
Helpful business/productivity applications:
• Anagram (captures data from email signatures and adds into your contacts)
• Action Pad (currently in beta) replacing your original Memo Pad (not to be deleted though)
• Copy All: able to copy a complete email simply & quickly
• Save Number as: instead of the default saving number as work number, this one provides you with home, mobile or work options.
• Forward with edit: allows you to edit an email prior to forwarding onto someone else.
• Onto task: turns a received email into a task, which then in turn, synchronises with Outlook.
• Onto calendar: turns a received email into a calendar entry, which in turn, synchronises with Outlook.
• Remind Me Later: a simple added menu option to remind you of a call, SMS, email, appointment at a later time.
• Send Timely SMS: never forget an important anniversary ever again. Program in a message and time its delivery...set and forget.
• QuickLaunch: assign a hot key to quickly access the myriad of applications installed on your BlackBerry
• IntelliLaunch: a search function for anything that is stored in your BlackBerry whether it is the internal memory or on the SD Card. Also shows battery life and BlackBerry PIN
• MindBerry: mind mapping on your BlackBerry and exportable to your laptop/PC
• QuickPull: quickly and easily do a soft reset of your BlackBerry without having to complete a battery pull.
• WhatsApp: allows other who are connected to you to see if you are available, without having to ask (@WhatsAppInc on twitter).
• Google Maps: self explanatory.
• Vlingo: voice activation. You can create emails, SMS others, create tasks, remind yourself, call people, search for things, as well as post to twitter and Facebook, all of which activated by one hot key.
Inbuilt applications in the BlackBerry that may not be commonly used:
• AutoText: a simple way of creating words/phrases/signature panels/whole sentences simply by keying a couple of letters into an SMS, email, SocialScope, BlackBerry Messenger etc, and hitting the space bar (eg. "pif" becomes #payingitforward from my AutoText list)
• Tasks: anyone who practices the 4D's (delete, delegate, do it, & date activate) with time and workload management, would welcome the Task folder, which synchronises perfectly with Outlook.
• BlackBerry Messenger: a BlackBerry to BlackBerry (or PIN to PIN) messenging service: quick, simple and free. Like Instant Messaging, it requires other users to accept you as a contact.
This is the list of applications that I use on a daily basis... I haven't provided links to everything here, but as they say in the classics... google is your friend.
I hope it helps you also.