Honestly, if its a small business, Windows 2003 Server will work just fine. Couple that with Group Policy and you've got a nice, out of the box solution.
I use Citrix Presentation Server 4.0 at my day job. I will tell you that Citrix can handle much larger user loads than Terminal Server. In addition, it has very bandwidth friendly connections (roughly 8 times 'thinner' than RDP). The printing in the newer version has been greatly improved as well (it used to be a nightmare in 1.8).
I support roughly 500 remote users at over 50 branches over 768k lines at each location. We publish Office (Access & Outlook incl), MS IE, and a wholoe host of other critical apps (61 at last count). I can tell you that with this type of load, Citrix is the way to go.
Sure there are some open source apps and some others like Tarantella, but what kind of support do they offer? Yeah I know the open source community is around to help, but for critical applications (like ours), I'm not going to rely on the community solely to help.
Do some Googling for Network World's review of remote application suites. They had some nice info in there.
Good luck in your choice.