Depends on the cell types, species and data types you're interested in.
For very specific data sets, you can always give GEO and the SRA a chance where most people submit their data when publishing a paper. You could, for example, simply search for "ChIP-seq CD8" and have a look whether anything relevant pops up. The advantage of using data from consortia such as Blueprint is that their data generation and processing should be highly standardized which you cannot always expect from data submitted by labs that perhaps have never done ChIP-seq before.
Consortia similar to Blueprint are Roadmap and IHEC - most of these consortia consist of smaller subgroups that tackle very specialized tasks, e.g. the German contribution to IHEC (DEEP) focuses on human and mouse cells relevant for chronic metabolic and inflammatory diseases.