Benefits of the Barclays Cash ISA include:
Can be opened from just £1.
Interest calculated on daily statement balances and credited annually.
Instant access to your cash (once you deposit the maximum ISA allowance you cannot replace what you withdraw).
ISAs allow tax free savings; they run from tax-year to tax-year (ie 6 April one year to 5 April the next) and interest is paid tax-free.
You can compare Barclays Cash ISAs with other leading providers in the tables.