ACA. Offered: Almost entirely in practice, though there are a few audit based positions in industry and the public sector. Rarely offered outside the UK. Syllabus: Strong on tax, audit, financial reporting. Weak on finance, management accountancy, management theory. Centered around skills needed by practice: statutory work, and giving advice to external clients. Recognised qualification for statutory audit/insolvence.
ACCA. Offered: Offered in industry, practice and the public sector. Very strong internationally. Syllabus: Good all round, optional papers give you ability to customise qualification (and includes international papers): though not as strong on tax/audit as ACA, or finance/management as CIMA, whatever you choose. Qualification is more technical and less focused on particular working skills - e.g. no Case Study. Recognised qualification for statutory audit/insolvence.
CIMA. Offered: In industry and the public sector. Fairly strong international presence. Syllabus: Strong on finance, management accountancy, corporate strategy; weak on financial reporting, audit, almost no tax. More mathematical/financial than the other two, less focused on statutory aspects. Centered around working within a company to advise management. Some accounting careers options (statutory audit/insolvency) not open, others (financial reporting, internal audit) may be difficult to get into with this qualification, but on the other hand it's far stronger than the other two on MBAish aspects of the syllabus.