What "NoSQL" database engines support dynamic / advanced queries in a similar fashion to MongoDB (http://www.mongodb.org/display/DOCS/Advanced+Queries) ?
Specifically interested in options that support ad-hoc querying from a shell or within client languages.
None just use MongoDB ;)
Honestly, it really depends on what type of querying you plan to do. For Key/Value style queries where you plan to just pull up one document at a time, then basically all of the NoSQL DBs are good for this.
When it comes to pulling back "sets" of data or using alternate keys, then MongoDB is probably your best "crossover" here. Many NoSQL DBs have limited querying functions, especially on non-key fields. Of course, that's kind of the point of "Key-Value stores", so Mongo is kind of a mutant here.
The last I checked with Cassandra, there was definitely some "hoop-jumping" involved to really support ad-hoc non-key queries. And CouchDB seems to point to "just Map / Reduce".
That stated, I believe that there is motion from several NoSQL dbs to support such ad-hoc querying mechanism. So this answer could be completely wrong in 2 months :)