Anything that leads to aspiration of bodhicitta (aspiration to attain awakening) is useful here. For example, the Diamond Sutra, very commonly studied in Chan.
can you recommend any online translations?
Astus has pointed to Chuck Muller's, which is from Kumarajiva. It's pretty good. Although I have been going around with the Skt in my backpack for the past few months, if you are interested in Chan, then Kumarajiva's translation is the one to use. If I recite, I recite Kumarajiva's. If I study, then I read them all, Sanskrit first! haha.
Recently I taught a semester on the Diamond Sutra at our Foguang Shan center in Hong Kong, Kowloon side. I've been giving special emphasis to the vows at the start of the sutra. In Muller's translation, it is this part: 3. The Bodhisattva's Vow
The Buddha said to Subhūti: "The bodhisattvas and mahāsattvas should subdue their thoughts like this: All the different types of sentient beings, whether they be born from eggs, born from a womb, born from moisture or born spontaneously; whether or not they have form; whether they abide in perceptions or no perceptions; or without either perceptions or non-perceptions, I save them by causing them to enter nirvana without remainder. And when these immeasurable, countless, infinite number of sentient beings have been liberated, in actuality, no sentient being has attained liberation. Why is this so? Subhūti, If a bodhisattva abides in the signs of self, person, sentient being, or life-span, she or he is not a bodhisattva."
The "All ... sentient beings ... I save them by causing them to enter nirvana without remainder" is the part I call "bodhicitta with signs". It has the signs of a living being to be saved, and a bodhisattva who saves them. This perspective helps arise compassion and strong motivation.
The "And when these ... sentient beings have been liberated, in actuality, no sentient being has attained liberation ..." is the part I call "bodhicitta without signs". No perception of a living being to be saved, or a bodhisattva to save them. This is the arising of wisdom, the wisdom of emptiness or not self.
Muller uses the term "sign", as do I, although other versions of the text, including the Skt, use the term "samjna" = "perception". The difference is not that great. Based on a sign one arises a perception, or rather, when one has a perception one assumes that there is a sign. I used to make a big deal out of the difference, but nowadays I've come to see the meaning behind this, not just the words.
This vow - bodhicitta - is the true compassion. All the other compassionate activities of a bodhisattva are based on this.