As much as I love basecamp, I think it is still a little pricey for me, and I'm just not doing cartwheels yet with the way basecamp has designed their interface. My custom invoice templates, emailing, dropbox app, we transfer are all ghetto fabuous. I use paypay for credit card payments, and I have a hidden link on my site, designated for my clients when they need to pay me with a credit card. If I'm more of a product based business, getting a credit card account set up would be ofcourse essential.
I've been watching a company called http://www.projectbubble.com, and I'm working with a book-keeper, that has helped me tremendously with managing my money. Recently, I've also discovered some cool little widgets thats been helping me here and there, a free program called sidenote, and this is free to download, if you have Evernote on your iphone, this is similar as a stickies version for your laptop, (site to download: http://www.chatelp.org/?page_id=5 ), also another application called: http://www.potionfactory.com/thehitlist/ has been great with managing my todos, and delegating tasks. It's also free to download.
On the philosophical note about this post, my new business management model has been interestingly challenged this past couple of years due to a southern husband, child, and a dog that belongs in the circus. This link not sure if its related to this conversation thread or not, but surely will help anyone that owns a business, speaks more of time management, which I think is core of all this: Dan Sullivan, and his blog post here: (http://srfinctr.wordpress.com/2010/04/13/the-entrepreneurial-time-system) talks about a way to divide owning your business in three sections: Free Day, Focus Day, Buffer Day. I haven't really initate this system yet, but its essential that I start soon.