Like Quicken:
http://kmymoney2.sourceforge.net/
http://www.gnucash.org/

Very powerful and robust, like Quickbooks:

http://www.sql-ledger.org/

See also: www.desktoplinux.com/articles/AT2282537026.html (this is
old, but I checked Codeweavers and quickbooks sort of works in Linux)

www.codeweavers.com/.../?letter=q;

Hover over the Codeweavers icons to find out what they mean.

This application is considered by many to be the single biggest drawback to
switching to enterprise Linux due to Quickbooks' prevalence in small
business and the lack of file compatibility. You can always go the
VirtualBox route.

I have been trying to make the switch to GnuCash. I have been just using it for
my personal stuff. I haven't tried it for a company. I don't know if it will do
payroll or not. It will print checks but you have to use certain stock. I don't
try to print checks with it yet.

If you have been using QB for 5 years then you will have quite a learning curve
by switching to Gnucash. I keep Windows XP around just for running QB. Most
businesses in my area don't even know what Linux is. They all run Windows. I am
quite rural, though.

Intuit keeps talking about coming out with a Linux version but I will believe it
when I see it. Recently the tax tables are over $400/year when you use them for
doing payroll with QB. The program can be bought for around $100 sometimes. They
get you with the tax tables for your payroll. When I first started using QB for
payroll the tax tables were less than $200/year.

I don't know that much about databases or sql for
that matter. For that reason I have tried to go with something that I
understand. I will download and SQL-Ledger and the readme file and have a look
at it. Gnucash is doing the job for me so far. I don't know how much it
resembles Quicken. I have never used Quicken.

Does Gnucash do payroll (for USA)? I had the impression it did not so I never
looked any closer.

Not sure myself. I have never used it for a business. I am just using it for my
personal stuff.

The first comment here http://www.linux-mag.com/id/6779 says that Gnucash does
not do payroll.

Money Dance is a good accounting package. Works in linuxs and the other
2 op sys too.

And here's the URL. http://www.moneydance.com/

I went to the web site. I couldn't find out whether or not is uses double entry
accounting practices or not. Gnucash does.

From what I saw it seems that Moneydance might be along the lines of Quicken or
MSMoney.