Hello, we are planning a trip to the outer Hebrides in June. Going to rent a cottage on Lewis and use that as a base for exploring. Plan to go to St. Kilda one day if weather cooperates. I would like to go to Skye but car hire places on Lewis do not allow cars to be brought to the other islands; also, ferry schedule is such that if we took the ferry from Talbert to Uig one day we would have to turn around and come back 3 hours later. Should we plan an overnight on Skye? Also planning to travel down Uists and stay on Barra 2 nights. Is car really necessary there? I keep reading that it is but road is only 12 miles around. Anyone been to Staffa? Interested in going there but not planning to go to Mull so would need to go from Oban after taking ferry from Barra and it would be a long day. worth it to add that on? Thanks!

Where are you starting this trip from? If starting from the mainland you could drive (or take a bus) to Skye to begin your trip, spend one night there (there is far too much to see there not to), I would advice two nights, especially when relying on public transport. Take the ferry from Uig, see Lewis and Harris and work your way down over the Uists to Barra. Are you planning to stop anywhere on the Uists? because in one day you won't have time to see anything, except what you drive past which seems a shame.
On Barra you do not really need a car, do note that while the 'ring road' is only 12 miles around, there are a lot of little roads beside that and things you want to see may be down those roads, which can add a few more miles. That being said, the buses are really quite good during the summer and I've visited a few times without a car (but I like hiking and take my time). See if you can go to Vatersay while on Barra, amazing beaches that are well worth the side trip.
I'm not sure how you are planning to get to Staffa without going over Mull. From Oban it can only be done with organised day tours, as far as I'm aware, which usually offer more than just Staffa. When making the effort to go out there I would also take in Iona (there are tour options that allow that) which is wonderful. Landing on Staffa is weather dependent and it's not really wort it going out there if you can't land.
In general, don't underestimate how much time it takes to do these things by public transport, I get a feeling you might be underestimating things a bit. It is perfectly possible, but it takes time.

Staffa is impressive if the weather is so so (the boat trip not for the feeble-stomached...), but one is never sure landing will be possible: leaping onto a slippery "dock" and visiting the grotto on uneven, even more slippery rock, and scambling up the wind-beaten top of the cliffs is unforgettable.
Can be coupled with a day trip to Iona, very nice place.
There are amazing beaches in the Hebrides, You won't regret it.

We are flying from London to Stornoway and staying on Lewis for a week. Planning to use Lewis as base for exploration as I would like to go to St. Kilda and it seems that it might take a week (if even possible at that) to get good enough weather to make the trip. I plan to rent a car on Lewis and then use public transportation to get down the Uists. I do want to spend time there but have a room booked for 2 nights on Barra and not sure about the day or 2 in between. Don't want to underestimate time needed. I realize I can't make it to all the islands. Sounds like a car on Barra is a good idea for greater exploration.

I would not dismiss the bus and ferry option. It is very comprehensive and link in with the ferries and flights. We have used it several times particularly through Barra and the Uists. On Barra there is access to Vatersay by bus. The Council's website is useful - http://www.cne-siar.gov.uk/travel/busservice/current/index.asp
R

Visiting St Kilda is a lottery. If the weather's bad, the boat won't run. And the places on the boat fill up months in advance, so if you miss your day, you're just unlucky - you can't just pop along the next day instead.
The Outer Hebrides are much bigger than you'd think, and the roads are twisty and can be hilly in Harris and Barra. A car would be sensible. Public transport is infrequent so if you want to take a bus then you'll need to schedule your whole day around their timetables. Buses also don't tend to go to the end of the road - and half the fun of the Outer Hebrides is taking single track roads and seeing where they end up.
If you hire a car in Lewis, you can take it to the other islands without anyone stopping you, but you will need to get the car back to Lewis and be aware that if your car breaks down in the Uists or Barra, you'll have to get it back to Lewis at your own expense.

Ugh I just realized I made a terrible mistake! I booked the hostel in Barra on a Sunday, thinking I would take the bus from South Uist and catch the ferry... but of course the bus doesn't run on Sunday (for some dumb reason I thought there was just no bus service on Lewis and Barra...) I have no idea what I am going to do now.. I have all these places booked and no way to get to Barra! Any ideas? Is there car rental on the Uists? I really didn't want to do that but maybe it is my only way. But do the ferries even run on Sunday? Summer schedule I can't find yet.

Summer timetables are online now (http://www.calmac.co.uk/timetables/calmac-summer-timetables.htm) but there is no Lochboisdale-Castlebay ferry on Sunday. If you can get down to Eriskay, the Eriskay- Barra ferry does run on Sunday, but getting to Eriskay might be the issue. Sunday is still a proper day of rest on the outer hebrides, so regardless of where you are, plan a day outside (everything will be closed), with some hiking and make sure you buy food for the day on Saturday.
I would see about cancelling the Sunday night in Barra, you are still far ahead of time, so they will probably not charge you the full night for cancelling if you explain the issue. There is a ferry on Monday morning from Lochboisdale to Castlebay, which will get you to Barra at 9am, which leaves you the full day on Barra. It seems like the more practical option.