Integration with QuickBooks mentioned by Ivan P. Graphs would be good.

Intermediate search capability to be added above search results and filters. This will complement the existing filtering search which is to be moved just above search results. Use combined icon for filtering and search.

Show detailed information for list items. Include organizations in sell-items, and much more.

Add ratings to each market-item. Average (or find median, etc) rating across organizations and general items.

Include the number of items for each category beside it.

Have an option to edit specific items, organizations, availability profiles, and your profile.

Save the user's selections to localStorage and the user account. This includes data for what page a person is on (general item, specific item) and filter selections.

Have a link to bookmarks at the top of the shopping cart page. Allow users to bookmark general items and specific items, and possibly market items.

On full-size screens, move the filter settings to the left-hand side of the screen beside the general item listings and specific item listings when filters are set up there.