I just signed up to Digital Ocean and used this promo code for $40 credit, they make you give Credit Card details first to verify who you are supposedly but its still a nice way to test things out.
Whilst the code doesn't specify, as far I can tell this looks like the type of promo code that should work for everyone (or at least those who haven't redeemed any code previously) and it looks like it has an expiry of June 1st.
It does not combine with the referral program ($10 credit). One or the other, as it seems like they have a system of redeeming one promo for the life of your account.
As far as the product goes they seem to be an ok mix between speed/cost/bandwith if that's what you are looking for, this is pretty hard to find from Australia.
Their $5US a month package includes:
512mb memory
1 core processor
20gb ssd
1tb transfer
It scales up from there with several more plans below $40 and quite a few above that cost per month.
You can conduct speed tests for the various datacenters here