The links below have instructions for deleting photos.
iOS and iPod: Syncing photos using iTunes
iPad Tip: How to Delete Photos from Your iPad in the Photos App
Another Way to Quickly Delete Photos from Your iPad (Mac Only)
How to Delete Photos from iPad
How to: Batch Delete Photos on the iPad
(With iOS 5.1, use 2 fingers)
How to Delete Photos from iCloud’s Photo Stream
I found this post about deleting photos from the iPad and it is what finally worked for me quickly and easily, even for a large # of photos. Sorry that I can't remember quite where it came from but I hope this helps others!!
How to delete photos from your iPad
When you connect the iPad to your Mac or PC and open iTunes, after a few seconds the iPad will appear in the left-hand column under a heading of "DEVICES". Click the iPad once to select it. The right-hand iTunes panel will show properties of your iPad once it is selected. Along the top of the properties panel are tabs. Click the "Photos" tab. If you have already sync'ed photos from your computer, then the "Sync Photos from" checkbox will already be selected. To prevent every photo from your computer’s “Pictures” or “My Pictures” folder from syncing to the iPad, you need to click the arrowhead icon in the field that names where the "Sync Photos from" location is. Clicking the arrowhead icon opens up a selection menu where you should choose “Choose folder . . .”. A “Change Photos folder location” window will appear that you can use to create a new folder, highlight the folder by clicking on it, and clicking the “Choose folder” button. The name of the new folder I created when I used this process was something descriptive, the “iPad photo sync” folder. Make sure that the “All folders” radio button is selected.
When you change these settings, iTunes will create “Revert” and “Apply” buttons in the bottom-right corner. Click the “Apply” button to save the settings. This will also remove all of the added photos from the iPad that are not part of the Camera Roll, or all of the previously synced photos.
You can now copy all of the photos you want on the iPad to the new folder (the “iPad photo sync” folder in my case.) You can arrange the photos into subfolders, but do not create more than one subfolder deep in the new iPad photo sync folder or the iPad will be unable to display the subfolders of subfolders. This also means that your PC will have two copies of the photos, the original in the “Pictures” or “My Pictures” folder, and the copy for the iPad in the “iPad photo sync” folder.
Don’t want two copies of each iPad photo on your PC? Instead of creating a unique “iPad photo sync” folder, leave the “Pictures” or “My Pictures” folders selected in the "Sync Photos from" location, and unselect the “All folders” option by choosing the “Selected folders” option. With this option in place, you can then select specific subfolders from your “Pictures” or “My Pictures” folders. The downside is that you can only select whole folders at a time and not individual images.