I have been used to Trados' TagEditor, but I believe other major tools, Trados, Deja Vu, Across, Idiom, are as good for this purpose.
I would advise against using Across, at least if you want to keep your translators happy. It isn't a proper modern CAT tool from a translator's perspective, it's a lot slower to work in compared to the other options in your list. Across is free, but any professional software translator should own a better CAT tool.
From a former software developer's point of view, I personally do not recommend dedicated software localization tools such as Alchemy Catalyst. They behave more like toys than professional tools.
[Edited at 2012-06-09 01:21 GMT]
This has been my experience, as well. I don't think there's enough differences between string translation and other types of translation to warrant a whole different line of CAT software (at least nowadays, when the generic CAT tools are full of all kinds of features).