Finance Minister Máirtín Ó Muilleoir made the announcement in a reallocation of funds known as a monitoring round.
The SHA allowed Stormont to borrow money for a public sector redundancy scheme but any under spend can be used for capital projects.
Half of the £30m will be used for roads maintenance.
In total, the redundancy scheme is set to be under spent by around £100m this year.
However, only £30m has been reallocated as it will be difficult to start new capital projects this late in the financial year.
The largest portion of the money, £15m, will be used for roads maintenance; £10m will be spent on approximately 45 new buses.
The remaining £5m will be used for a new community regeneration fund.
The minister said this will be for "small scale but focused interventions in our most deprived and marginalised communities."
"We need long-term economic stimulus and I envisage this will be delivered by our executive in the near future.
"We are sending an early signal of intent."
Other reallocations include £13m for schools maintenance and £8.7m to the Department of Health for essential maintenance and defibrillators for ambulances.
There is also a £2.5m allocation to the Department of Economy for route development at the City of Derry Airport.
The minister also noted that £20m has been set aside this year to cover the cost of the botched Renewable Heat Incentive scheme.
That additional annual cost is likely to reoccur every year over the 20-year life of the scheme.
A £30m 'stimulus package' has been announced funded by borrowing powers made available under the Stormont House Agreement (SHA).