This really depends on what you actually need from your office apps.

Theres a couple good Writing/Word Processing apps in the Ubuntu Software Center. AbiWord, LyX Document Processor, and Zoho Webservice Word Processor (Ordered from best and pretties, to leasts in my opinion) But I personly use one called "FocusWriter". I really like it cause its very very simple, you can set a background image to be behind your typing, and when started it automatically starts in fullscreen. Its not available in the Software Center, but can easily be installed by following the tutorial a the bottom of this article about FocusWriter. FocusWriter on OMG Ubuntu!!

There only 2 stand alone spreadsheet apps I find in the Software Center are Gnumeric and Zoho Webservice Spreadsheet. I haven't touched a spreadsheet since I was in middle school, which was a good LONG time before I came to using Linux. So maybe there are other spreadsheet apps out there that I don't know about.

But as far as a stand alone presentation app goes, I don't know of any really sinces again I don't ever make presentations. I know Scribus pops up when searching the Software center for presentation apps, and I know the "Full Circle Magazine" alot to layout their very professional looking publication. I don't know if it can be used to output documents in a presetation format though. Zoho Webservice Presentation is there too so if all else give it a shot. Anyone with more info on this part please chime in.

Now if you want a all included Office Suite. Open Office is still available through the software but not popular cause of all the drama over Oracle being greedy. A good alternative might be KOffice though.

Sorry if I was too long. But hope I helped.