Accounting software for small businesses and sole traders can be nightmarishly complicated and full of jargon. Sage's new web-only accounts service has been designed to remove much of the complexity, yet be powerful enough to cope with most situations. You can read my review of the £12-a-month Accounts version (there's a cheaper £6-a-month service for cash-based businesses called Cashbook) over on Computeractive.
Note that in the review I mention the missing invoice batch payment facility for use when a payment covers multiple invoices; after the review was published Sage pointed out that this feature does exist, but it is poorly exposed (a hidden checkbox appears when you hover over an unpaid invoice entry, and selecting this lets you add it to a batch receipt job). This is rather poor usability for a common task, and Sage says it plans to look at how to improve this feature.