What is it? Unfuddle is by far the best and easiest project management tool I have used to this point. It allows you to track the project conversation, tickets for bugs, new enhancements, or just things to do; milestones (and the progress made towards their completion); as well as project documentation. One of the greatest points though that many other similar sites do not offer, is that Unfuddle gives you an SVN repository along with your project and can send notifications to team members when updates are checked in. The dashboard gives you a quick glance at everything going on with the project and the whole system is very usable.
What does it cost? At the time of this post, plans range from free to $99 per month. Your choice depending on the needs of you and/or your team.
What is it? I'd be surprised if you've not had a development question you've googled and not ran across it on StackOverflow. This is an excellent resource for asking questions to other developers (and helping to answer them) to get your issues resolved. What I believe is the best feature of the site is the ranking system. For well answered questions you receive points. What this means to the asker of the question is that those users out there attempting to gain "karma" on the site are going to answer your question to the best of their ability.
What does it cost? Totally and utterly free!
What is it? For consultants like myself, this is the best time tracking and invoicing application there is. Period. There is even an app on the iphone that you can use to track hours for your clients which is very useful. The site itself is easy to use. It allows you to brand your logo on the invoices, send them via snail mail or email, share documents, and there are many reporting options to see where you are financially.
What does it cost? Plans range from free to $149 per month.
What is it? There are many times when I need to send a large file to a client or colleague and email servers can often times limit the size of attachments. BuckleFish allows you to send any file to anyone, anytime. It is currently in beta and limited to 1Gb per file, but I can't remember ever needing to send a file that large.
What does it cost? Absolutely free!
What is it? Ever heard of GotoMeeting? Well, this is it's free counterpart. Maybe not as full featured, but also not as pricey. The functionality is almost identical minus a few bells and whistles. This product is an absolute must have for remote meetings, customer support, and other web conferencing needs.
What does it cost? Like I said... nada!
Final Thoughts... I use each of these products multiple times a week, sometimes more. I cannot say enough about how they help me through my days. A huge thanks to all the developers that put these products out there for us.