You can contribute your XHT to towards other exchange projects in a method called multi-party collateralization. Alternately you can create your own exchange and open it to others to help your exchange get collateralized.
To find places to use your XHT you can visit the project page found at dash.bitholla.com/projects. There you can find selected few featured projects and a search function.
Note, only after the target amount is met will the XHT collateral be locked and staked. Before the collateral target amount all participates are free to withdraw their pledge.
After target collateral is met and the amount is locked, to withdraw a majority vote is required to unlock the XHT.