The ISA rules changed dramatically in that budget, raising the ISA allowance by more than ever before. In fact, not only did the 2014/15 ISA limits increase but the ISA itself has now changed too. It is now officially a NISA (New ISA) which means there is no more Cash ISA or Stocks and Shares ISA. There is just one type of ISA now.
Because there is only one type of ISA now you can actually save as much as £15,000 into what you and I would call a Cash ISA, or you can invest up to £15,000 into the old Stocks and Shares ISA. The alternative is that you do a bit of both, as long as you stick to the overall limit of £15,000.
The allowance for Junior ISAs is now £4,000. This limit also applies to Child Trust Funds (CTFs). You cannot merge a CTF and Junior ISA (yet) but may be able to in the near future. Until then you cannot hold both types for any one child either. Your child has to have either one or the other for the time being.