The mavic XM819 or XM719 are designed to take upto 2.3 tyres, they will cope fine with 2.4 as neil853 mentions above.
Stans ZTR Crest are a littel wider and a little lighter and would give you more tyre volume but you would have to add a tubeless rim strip to run tubelss which will even the weight out with the mavic rim a fair bit.
If you have had no real problems with your curent setup (dinged rimms or buckled wheels) then any of the above options would suit, if you feel you want something a bit stronger then the Stans ZTR Flow rim is wider and heavier still but will be a bit stronger too.
[hijack] If you need a 240 front hub drop me an email I have one that has sat in my flat for the last year i could do with selling [/hijack]