What is the aggregate maximumfor non-cash charitable contribution to multiple charities? For example, clothing to four different charities totaling $1900.

[Opus 17]

There is no aggregate maximum.  If your non-cash donations are more than $500 you need to include an extra form 8283 -- Turbotax will do this for you.  If you donate a single item or group of similar items with a value of more than $5000, you must have a signed appraisal and the appraiser and a representative from the charity must sign a copy of form 8283 that you must mail to the IRS.