I found a great tool to be used with businesses a few weeks back.
Update Log is a great place to manage all of your projects and set check lists for yourself. You can setup the free version and give it a shot. If you feel more ambitious you could try the paid version. The nice thing is this runs all off of the internet browser and you can give access to your employees as well as your customers!
Yes, Basecamp is definately an awesome tool when you need to collaborate with your clients on your projects. I would recommend any freelancer to at least give this a look and see if it meets your needs. Free is always good.

Glad to see others use this great application as well.
Hi!
It all depends on what functions you need. If you want just a friendly chet, then Basecamp is really the tool for you. But if you want to actually get things done you should look for something else. I'm using
Wrike.com. It's also web-based, but it's more about completing your projects, not just communicating on them.
Hi Hurry,
The link you posted wasn't working for me but I was able to figure it out.
http://www.wrike.com/ If you don't mind me asking, what plan are you using?
Thanks for the information!
No, I don't mind, Andy
I work in a team, but it's rather small. We started from the $5 individual plan, I guess they call it "power user" or something. It was used by the team leader. All the other members were subscribed to the free versions. Now we've upgraded to the 15-users plan, cause we feel we need more storage space, as we put more and more projects and tasks into Wrike.
The cool thing is you can invite as many people there as you like, including your clients and partners, and you won't need to pay, they will use the free versions.
Hi Hurry,
The link you posted wasn't working for me but I was able to figure it out.
http://www.wrike.com/ If you don't mind me asking, what plan are you using?
Thanks for the information!
Has anyone been able to contact them? I clicked on the contact us link at the top of the page and continued to complete their form but I wasn't able to send it... None of the buttons on the form worked. Anyone else have this problem?
Another great tool to use...Project 360
This offers all the benefits you will need to collaborate with clients online...
http://www.project360.com
Alternatively, I use a GPL script called dotproject. I customized it and serve it from my site, makes it VERY easy for clients to review tasks, projects, due dates, etc. I have a link to it from my site so it's all taken care of by my site.
http://www.dotproject.net/