For High-level:

getAllAccounts() - possibly with filtering parameters and sort/limit

I'm not sure what the Account object provides currently, but these would be useful:

getBalance()
getTotalTransferAmounts() - returns total amount of NXT transferred.  filter by in/out
getTransactions() - filter by activity type (in/out/alias creation/etc.)
getTimeFirstActivity() - filter by activity type (in/out/alias creation/etc.)
getTimeLastActivity() - filter by activity type (in/out/alias creation/etc.)
getBlocksGenerated() - correct term?
getFeeEarned() - correct term?
getAliases()